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<!DOCTYPE HTML> <html lang="en" class="light" dir="ltr"> <head>  <meta charset="UTF-8"> <title>Protocols - everything curl</title>  <meta name="description" content="everything there is to know about curl, libcurl and the cURL project"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="theme-color" content="#ffffff"> <link rel="icon" href="../favicon.svg"> <link rel="shortcut icon" href="../favicon.png"> <link rel="stylesheet" href="../css/variables.css"> <link rel="stylesheet" href="../css/general.css"> <link rel="stylesheet" href="../css/chrome.css"> <link rel="stylesheet" href="../css/print.css" media="print">  <link rel="stylesheet" href="../FontAwesome/css/font-awesome.css"> <link rel="stylesheet" href="../fonts/fonts.css">  <link rel="stylesheet" href="../highlight.css"> <link rel="stylesheet" href="../tomorrow-night.css"> <link rel="stylesheet" href="../ayu-highlight.css">  </head> <body class="sidebar-visible no-js"> <div id="body-container">  <script> var path_to_root = "../"; var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? 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document.getElementById("sidebar-toggle-anchor"); if (document.body.clientWidth >= 1080) { try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { } sidebar = sidebar || 'visible'; } else { sidebar = 'hidden'; } sidebar_toggle.checked = sidebar === 'visible'; body.classList.remove('sidebar-visible'); body.classList.add("sidebar-" + sidebar); </script> <nav id="sidebar" class="sidebar" aria-label="Table of contents"> <div class="sidebar-scrollbox"> <ol class="chapter"><li class="chapter-item "><a href="../index.html"><strong aria-hidden="true">1.</strong> Everything curl</a></li><li class="chapter-item "><a href="../how-to-read.html"><strong aria-hidden="true">2.</strong> How to read</a></li><li class="chapter-item "><a href="../project/index.html"><strong aria-hidden="true">3.</strong> The cURL project</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../project/started.html"><strong aria-hidden="true">3.1.</strong> How it started</a></li><li class="chapter-item "><a href="../project/name.html"><strong aria-hidden="true">3.2.</strong> The name</a></li><li class="chapter-item "><a href="../project/does.html"><strong aria-hidden="true">3.3.</strong> What does curl do?</a></li><li class="chapter-item "><a href="../project/comm.html"><strong aria-hidden="true">3.4.</strong> Project communication</a></li><li class="chapter-item "><a href="../project/etiquette.html"><strong aria-hidden="true">3.5.</strong> Mailing list etiquette</a></li><li class="chapter-item "><a href="../project/maillists.html"><strong aria-hidden="true">3.6.</strong> Mailing lists</a></li><li class="chapter-item "><a href="../project/bugs.html"><strong aria-hidden="true">3.7.</strong> Reporting bugs</a></li><li class="chapter-item "><a href="../project/support.html"><strong aria-hidden="true">3.8.</strong> Commercial support</a></li><li class="chapter-item "><a href="../project/releases.html"><strong aria-hidden="true">3.9.</strong> Releases</a></li><li class="chapter-item "><a href="../project/security.html"><strong aria-hidden="true">3.10.</strong> Security</a></li><li class="chapter-item "><a href="../project/trust.html"><strong aria-hidden="true">3.11.</strong> Trust</a></li><li class="chapter-item "><a href="../project/coc.html"><strong aria-hidden="true">3.12.</strong> Code of Conduct</a></li><li class="chapter-item "><a href="../project/devel.html"><strong aria-hidden="true">3.13.</strong> Development</a></li><li class="chapter-item "><a href="../project/devteam.html"><strong aria-hidden="true">3.14.</strong> The development team</a></li><li class="chapter-item "><a href="../project/users.html"><strong aria-hidden="true">3.15.</strong> Users of curl</a></li><li class="chapter-item "><a href="../project/future.html"><strong aria-hidden="true">3.16.</strong> Future</a></li></ol></li><li class="chapter-item expanded "><a href="../protocols/index.html"><strong aria-hidden="true">4.</strong> Network and protocols</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../protocols/network.html"><strong aria-hidden="true">4.1.</strong> Networking simplified</a></li><li class="chapter-item expanded "><a href="../protocols/protocols.html" class="active"><strong aria-hidden="true">4.2.</strong> Protocols</a></li><li class="chapter-item "><a href="../protocols/curl.html"><strong aria-hidden="true">4.3.</strong> curl protocols</a></li><li class="chapter-item "><a href="../protocols/http.html"><strong aria-hidden="true">4.4.</strong> HTTP basics</a></li></ol></li><li class="chapter-item "><a href="../install/index.html"><strong aria-hidden="true">5.</strong> Install curl and libcurl</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../install/linux.html"><strong aria-hidden="true">5.1.</strong> Linux</a></li><li class="chapter-item "><a href="../install/windows/index.html"><strong aria-hidden="true">5.2.</strong> Windows</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../install/windows/win-msys2.html"><strong aria-hidden="true">5.2.1.</strong> MSYS2</a></li><li class="chapter-item "><a href="../install/windows/win-vcpkg.html"><strong aria-hidden="true">5.2.2.</strong> vcpkg</a></li></ol></li><li class="chapter-item "><a href="../install/macos.html"><strong aria-hidden="true">5.3.</strong> macOS</a></li><li class="chapter-item "><a href="../install/container.html"><strong aria-hidden="true">5.4.</strong> Container</a></li></ol></li><li class="chapter-item "><a href="../source/index.html"><strong aria-hidden="true">6.</strong> Source code</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../source/opensource/index.html"><strong aria-hidden="true">6.1.</strong> Open Source</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../source/opensource/license.html"><strong aria-hidden="true">6.1.1.</strong> License</a></li><li class="chapter-item "><a href="../source/opensource/copyright.html"><strong aria-hidden="true">6.1.2.</strong> Copyright</a></li></ol></li><li class="chapter-item "><a href="../source/layout.html"><strong aria-hidden="true">6.2.</strong> Code layout</a></li><li class="chapter-item "><a href="../source/options.html"><strong aria-hidden="true">6.3.</strong> Handling build options</a></li><li class="chapter-item "><a href="../source/style.html"><strong aria-hidden="true">6.4.</strong> Code style</a></li><li class="chapter-item "><a href="../source/contributing.html"><strong aria-hidden="true">6.5.</strong> Contributing</a></li><li class="chapter-item "><a href="../source/reportvuln.html"><strong aria-hidden="true">6.6.</strong> Reporting vulnerabilities</a></li><li class="chapter-item "><a href="../source/web.html"><strong aria-hidden="true">6.7.</strong> Website</a></li></ol></li><li class="chapter-item "><a href="../build/index.html"><strong aria-hidden="true">7.</strong> Build curl and libcurl</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../build/autotools.html"><strong aria-hidden="true">7.1.</strong> Autotools</a></li><li class="chapter-item "><a href="../build/cmake.html"><strong aria-hidden="true">7.2.</strong> CMake</a></li><li class="chapter-item "><a href="../build/separate.html"><strong aria-hidden="true">7.3.</strong> Separate install</a></li><li class="chapter-item "><a href="../build/windows.html"><strong aria-hidden="true">7.4.</strong> Windows</a></li><li class="chapter-item "><a href="../build/deps.html"><strong aria-hidden="true">7.5.</strong> Dependencies</a></li><li class="chapter-item "><a href="../build/tls.html"><strong aria-hidden="true">7.6.</strong> TLS libraries</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../build/boringssl.html"><strong aria-hidden="true">7.6.1.</strong> BoringSSL</a></li></ol></li></ol></li><li class="chapter-item "><a href="../cmdline/index.html"><strong aria-hidden="true">8.</strong> Command line concepts</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cmdline/differences.html"><strong aria-hidden="true">8.1.</strong> Differences</a></li><li class="chapter-item "><a href="../cmdline/options/index.html"><strong aria-hidden="true">8.2.</strong> Command line options</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cmdline/options/short.html"><strong aria-hidden="true">8.2.1.</strong> Short options</a></li><li class="chapter-item "><a href="../cmdline/options/long.html"><strong aria-hidden="true">8.2.2.</strong> Long options</a></li><li class="chapter-item "><a href="../cmdline/options/args.html"><strong aria-hidden="true">8.2.3.</strong> Arguments to options</a></li><li class="chapter-item "><a href="../cmdline/options/negative.html"><strong aria-hidden="true">8.2.4.</strong> Negative options</a></li></ol></li><li class="chapter-item "><a href="../cmdline/help.html"><strong aria-hidden="true">8.3.</strong> Help</a></li><li class="chapter-item "><a href="../cmdline/versions.html"><strong aria-hidden="true">8.4.</strong> Options depend on version</a></li><li class="chapter-item "><a href="../cmdline/urls/index.html"><strong aria-hidden="true">8.5.</strong> URLs</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cmdline/urls/scheme.html"><strong aria-hidden="true">8.5.1.</strong> Scheme</a></li><li class="chapter-item "><a href="../cmdline/urls/auth.html"><strong aria-hidden="true">8.5.2.</strong> Name and password</a></li><li class="chapter-item "><a href="../cmdline/urls/host.html"><strong aria-hidden="true">8.5.3.</strong> Host</a></li><li class="chapter-item "><a href="../cmdline/urls/port.html"><strong aria-hidden="true">8.5.4.</strong> Port number</a></li><li class="chapter-item "><a href="../cmdline/urls/path.html"><strong aria-hidden="true">8.5.5.</strong> Path</a></li><li class="chapter-item "><a href="../cmdline/urls/query.html"><strong aria-hidden="true">8.5.6.</strong> Query</a></li><li class="chapter-item "><a href="../cmdline/urls/ftptype.html"><strong aria-hidden="true">8.5.7.</strong> FTP type</a></li><li class="chapter-item "><a href="../cmdline/urls/fragment.html"><strong aria-hidden="true">8.5.8.</strong> Fragment</a></li><li class="chapter-item "><a href="../cmdline/urls/browsers.html"><strong aria-hidden="true">8.5.9.</strong> Browsers</a></li><li class="chapter-item "><a href="../cmdline/urls/options.html"><strong aria-hidden="true">8.5.10.</strong> Many options and URLs</a></li><li class="chapter-item "><a href="../cmdline/urls/globbing.html"><strong aria-hidden="true">8.5.11.</strong> URL globbing</a></li><li class="chapter-item "><a href="../cmdline/urls/connreuse.html"><strong aria-hidden="true">8.5.12.</strong> Connection reuse</a></li><li class="chapter-item "><a href="../cmdline/urls/parallel.html"><strong aria-hidden="true">8.5.13.</strong> Parallel transfers</a></li><li class="chapter-item "><a href="../cmdline/urls/trurl.html"><strong aria-hidden="true">8.5.14.</strong> trurl</a></li></ol></li><li class="chapter-item "><a href="../cmdline/configfile.html"><strong aria-hidden="true">8.6.</strong> Config file</a></li><li class="chapter-item "><a href="../cmdline/variables.html"><strong aria-hidden="true">8.7.</strong> Variables</a></li><li class="chapter-item "><a href="../cmdline/passwords.html"><strong aria-hidden="true">8.8.</strong> Passwords</a></li><li class="chapter-item "><a href="../cmdline/progressmeter.html"><strong aria-hidden="true">8.9.</strong> Progress meter</a></li><li class="chapter-item "><a href="../cmdline/curlver.html"><strong aria-hidden="true">8.10.</strong> Version</a></li><li class="chapter-item "><a href="../cmdline/exitcode.html"><strong aria-hidden="true">8.11.</strong> Exit code</a></li><li class="chapter-item "><a href="../cmdline/copyas.html"><strong aria-hidden="true">8.12.</strong> Copy as curl</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/index.html"><strong aria-hidden="true">9.</strong> Command line transfers</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/verbose/index.html"><strong aria-hidden="true">9.1.</strong> Verbose</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/verbose/trace.html"><strong aria-hidden="true">9.1.1.</strong> Trace options</a></li><li class="chapter-item "><a href="../usingcurl/verbose/writeout.html"><strong aria-hidden="true">9.1.2.</strong> Write out</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/downloads/index.html"><strong aria-hidden="true">9.2.</strong> Downloads</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/downloads/whatis.html"><strong aria-hidden="true">9.2.1.</strong> What is downloading?</a></li><li class="chapter-item "><a href="../usingcurl/downloads/storing.html"><strong aria-hidden="true">9.2.2.</strong> Storing downloads</a></li><li class="chapter-item "><a href="../usingcurl/downloads/url-named.html"><strong aria-hidden="true">9.2.3.</strong> Download to a file named by the URL</a></li><li class="chapter-item "><a href="../usingcurl/downloads/content-disp.html"><strong aria-hidden="true">9.2.4.</strong> Use the target filename from the server</a></li><li class="chapter-item "><a href="../usingcurl/downloads/charsets.html"><strong aria-hidden="true">9.2.5.</strong> HTML and charsets</a></li><li class="chapter-item "><a href="../usingcurl/downloads/redirects.html"><strong aria-hidden="true">9.2.6.</strong> Shell redirects</a></li><li class="chapter-item "><a href="../usingcurl/downloads/multiple.html"><strong aria-hidden="true">9.2.7.</strong> Multiple downloads</a></li><li class="chapter-item "><a href="../usingcurl/downloads/browsers.html"><strong aria-hidden="true">9.2.8.</strong> My browser shows something else</a></li><li class="chapter-item "><a href="../usingcurl/downloads/max-filesize.html"><strong aria-hidden="true">9.2.9.</strong> Maximum filesize</a></li><li class="chapter-item "><a href="../usingcurl/downloads/metadata-fs.html"><strong aria-hidden="true">9.2.10.</strong> Storing metadata in file system</a></li><li class="chapter-item "><a href="../usingcurl/downloads/raw.html"><strong aria-hidden="true">9.2.11.</strong> Raw</a></li><li class="chapter-item "><a href="../usingcurl/downloads/retry.html"><strong aria-hidden="true">9.2.12.</strong> Retry</a></li><li class="chapter-item "><a href="../usingcurl/downloads/resume.html"><strong aria-hidden="true">9.2.13.</strong> Resuming and ranges</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/uploads.html"><strong aria-hidden="true">9.3.</strong> Uploads</a></li><li class="chapter-item "><a href="../usingcurl/transfers/index.html"><strong aria-hidden="true">9.4.</strong> Transfer controls</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/transfers/tooslow.html"><strong aria-hidden="true">9.4.1.</strong> Stop slow transfers</a></li><li class="chapter-item "><a href="../usingcurl/transfers/rate-limiting.html"><strong aria-hidden="true">9.4.2.</strong> Rate limiting</a></li><li class="chapter-item "><a href="../usingcurl/transfers/request-rate.html"><strong aria-hidden="true">9.4.3.</strong> Request rate limiting</a></li><li class="chapter-item "><a href="../usingcurl/transfers/compression.html"><strong aria-hidden="true">9.4.4.</strong> Compression</a></li><li class="chapter-item "><a href="../usingcurl/transfers/skip.html"><strong aria-hidden="true">9.4.5.</strong> Skip download if already done</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/connections/index.html"><strong aria-hidden="true">9.5.</strong> Connections</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/connections/setup.html"><strong aria-hidden="true">9.5.1.</strong> Setup</a></li><li class="chapter-item "><a href="../usingcurl/connections/name.html"><strong aria-hidden="true">9.5.2.</strong> Name resolve tricks</a></li><li class="chapter-item "><a href="../usingcurl/connections/timeout.html"><strong aria-hidden="true">9.5.3.</strong> Connection timeout</a></li><li class="chapter-item "><a href="../usingcurl/connections/happy.html"><strong aria-hidden="true">9.5.4.</strong> Happy Eyeballs</a></li><li class="chapter-item "><a href="../usingcurl/connections/interface.html"><strong aria-hidden="true">9.5.5.</strong> Network interface</a></li><li class="chapter-item "><a href="../usingcurl/connections/local-port.html"><strong aria-hidden="true">9.5.6.</strong> Local port number</a></li><li class="chapter-item "><a href="../usingcurl/connections/keepalive.html"><strong aria-hidden="true">9.5.7.</strong> Keep alive</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/timeouts.html"><strong aria-hidden="true">9.6.</strong> Timeouts</a></li><li class="chapter-item "><a href="../usingcurl/netrc.html"><strong aria-hidden="true">9.7.</strong> .netrc</a></li><li class="chapter-item "><a href="../usingcurl/proxies/index.html"><strong aria-hidden="true">9.8.</strong> Proxies</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/proxies/discover.html"><strong aria-hidden="true">9.8.1.</strong> Discover your proxy</a></li><li class="chapter-item "><a href="../usingcurl/proxies/pac.html"><strong aria-hidden="true">9.8.2.</strong> PAC</a></li><li class="chapter-item "><a href="../usingcurl/proxies/captive.html"><strong aria-hidden="true">9.8.3.</strong> Captive portals</a></li><li class="chapter-item "><a href="../usingcurl/proxies/type.html"><strong aria-hidden="true">9.8.4.</strong> Proxy type</a></li><li class="chapter-item "><a href="../usingcurl/proxies/http.html"><strong aria-hidden="true">9.8.5.</strong> HTTP proxy</a></li><li class="chapter-item "><a href="../usingcurl/proxies/socks.html"><strong aria-hidden="true">9.8.6.</strong> SOCKS proxy</a></li><li class="chapter-item "><a href="../usingcurl/proxies/mitm.html"><strong aria-hidden="true">9.8.7.</strong> MITM proxy</a></li><li class="chapter-item "><a href="../usingcurl/proxies/auth.html"><strong aria-hidden="true">9.8.8.</strong> Proxy authentication</a></li><li class="chapter-item "><a href="../usingcurl/proxies/https.html"><strong aria-hidden="true">9.8.9.</strong> HTTPS proxy</a></li><li class="chapter-item "><a href="../usingcurl/proxies/env.html"><strong aria-hidden="true">9.8.10.</strong> Proxy environment variables</a></li><li class="chapter-item "><a href="../usingcurl/proxies/headers.html"><strong aria-hidden="true">9.8.11.</strong> Proxy headers</a></li><li class="chapter-item "><a href="../usingcurl/proxies/haproxy.html"><strong aria-hidden="true">9.8.12.</strong> haproxy</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/tls.html"><strong aria-hidden="true">9.9.</strong> TLS</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/tls/ciphers.html"><strong aria-hidden="true">9.9.1.</strong> Ciphers</a></li><li class="chapter-item "><a href="../usingcurl/tls/enable.html"><strong aria-hidden="true">9.9.2.</strong> Enable TLS</a></li><li class="chapter-item "><a href="../usingcurl/tls/versions.html"><strong aria-hidden="true">9.9.3.</strong> TLS versions</a></li><li class="chapter-item "><a href="../usingcurl/tls/verify.html"><strong aria-hidden="true">9.9.4.</strong> Verifying server certificates</a></li><li class="chapter-item "><a href="../usingcurl/tls/pinning.html"><strong aria-hidden="true">9.9.5.</strong> Certificate pinning</a></li><li class="chapter-item "><a href="../usingcurl/tls/stapling.html"><strong aria-hidden="true">9.9.6.</strong> OCSP stapling</a></li><li class="chapter-item "><a href="../usingcurl/tls/clientcert.html"><strong aria-hidden="true">9.9.7.</strong> Client certificates</a></li><li class="chapter-item "><a href="../usingcurl/tls/auth.html"><strong aria-hidden="true">9.9.8.</strong> TLS auth</a></li><li class="chapter-item "><a href="../usingcurl/tls/backends.html"><strong aria-hidden="true">9.9.9.</strong> TLS backends</a></li><li class="chapter-item "><a href="../usingcurl/tls/sslkeylogfile.html"><strong aria-hidden="true">9.9.10.</strong> SSLKEYLOGFILE</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/ssh/index.html"><strong aria-hidden="true">9.10.</strong> SCP and SFTP</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usingcurl/ssh/url.html"><strong aria-hidden="true">9.10.1.</strong> URLs</a></li><li class="chapter-item "><a href="../usingcurl/ssh/auth.html"><strong aria-hidden="true">9.10.2.</strong> Authentication</a></li><li class="chapter-item "><a href="../usingcurl/ssh/knownhosts.html"><strong aria-hidden="true">9.10.3.</strong> Known hosts</a></li></ol></li><li class="chapter-item "><a href="../usingcurl/reademail.html"><strong aria-hidden="true">9.11.</strong> Reading email</a></li><li class="chapter-item "><a href="../usingcurl/smtp.html"><strong aria-hidden="true">9.12.</strong> Sending email</a></li><li class="chapter-item "><a href="../usingcurl/dict.html"><strong aria-hidden="true">9.13.</strong> DICT</a></li><li class="chapter-item "><a href="../usingcurl/ipfs.html"><strong aria-hidden="true">9.14.</strong> IPFS</a></li><li class="chapter-item "><a href="../usingcurl/mqtt.html"><strong aria-hidden="true">9.15.</strong> MQTT</a></li><li class="chapter-item "><a href="../usingcurl/telnet.html"><strong aria-hidden="true">9.16.</strong> TELNET</a></li><li class="chapter-item "><a href="../usingcurl/tftp.html"><strong aria-hidden="true">9.17.</strong> TFTP</a></li></ol></li><li class="chapter-item "><a href="../http/index.html"><strong aria-hidden="true">10.</strong> Command line HTTP</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../http/method.html"><strong aria-hidden="true">10.1.</strong> Method</a></li><li class="chapter-item "><a href="../http/response.html"><strong aria-hidden="true">10.2.</strong> Responses</a></li><li class="chapter-item "><a href="../http/auth.html"><strong aria-hidden="true">10.3.</strong> Authentication</a></li><li class="chapter-item "><a href="../http/versions/index.html"><strong aria-hidden="true">10.4.</strong> HTTP versions</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../http/versions/http09.html"><strong aria-hidden="true">10.4.1.</strong> HTTP/0.9</a></li><li class="chapter-item "><a href="../http/versions/http2.html"><strong aria-hidden="true">10.4.2.</strong> HTTP/2</a></li><li class="chapter-item "><a href="../http/versions/http3.html"><strong aria-hidden="true">10.4.3.</strong> HTTP/3</a></li></ol></li><li class="chapter-item "><a href="../http/post/index.html"><strong aria-hidden="true">10.5.</strong> HTTP POST</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../http/post/simple.html"><strong aria-hidden="true">10.5.1.</strong> Simple POST</a></li><li class="chapter-item "><a href="../http/post/content-type.html"><strong aria-hidden="true">10.5.2.</strong> Content-Type</a></li><li class="chapter-item "><a href="../http/post/binary.html"><strong aria-hidden="true">10.5.3.</strong> Posting binary</a></li><li class="chapter-item "><a href="../http/post/json.html"><strong aria-hidden="true">10.5.4.</strong> JSON</a></li><li class="chapter-item "><a href="../http/post/url-encode.html"><strong aria-hidden="true">10.5.5.</strong> URL encode data</a></li><li class="chapter-item "><a href="../http/post/convert-to-get.html"><strong aria-hidden="true">10.5.6.</strong> Convert to GET</a></li><li class="chapter-item "><a href="../http/post/expect100.html"><strong aria-hidden="true">10.5.7.</strong> Expect 100-continue</a></li><li class="chapter-item "><a href="../http/post/chunked.html"><strong aria-hidden="true">10.5.8.</strong> Chunked encoded POSTs</a></li><li class="chapter-item "><a href="../http/post/hiddenfields.html"><strong aria-hidden="true">10.5.9.</strong> Hidden form fields</a></li><li class="chapter-item "><a href="../http/post/browsersends.html"><strong aria-hidden="true">10.5.10.</strong> Figure out what a browser sends</a></li><li class="chapter-item "><a href="../http/post/javascript.html"><strong aria-hidden="true">10.5.11.</strong> JavaScript and forms</a></li><li class="chapter-item "><a href="../http/post/multipart.html"><strong aria-hidden="true">10.5.12.</strong> Multipart formposts</a></li><li class="chapter-item "><a href="../http/post/postvspost.html"><strong aria-hidden="true">10.5.13.</strong> -d vs -F</a></li></ol></li><li class="chapter-item "><a href="../http/put.html"><strong aria-hidden="true">10.6.</strong> HTTP PUT</a></li><li class="chapter-item "><a href="../http/redirects.html"><strong aria-hidden="true">10.7.</strong> Redirects</a></li><li class="chapter-item "><a href="../http/modify/index.html"><strong aria-hidden="true">10.8.</strong> Customize your HTTP</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../http/modify/method.html"><strong aria-hidden="true">10.8.1.</strong> Request method</a></li><li class="chapter-item "><a href="../http/modify/target.html"><strong aria-hidden="true">10.8.2.</strong> Request target</a></li><li class="chapter-item "><a href="../http/modify/fragment.html"><strong aria-hidden="true">10.8.3.</strong> Fragment</a></li><li class="chapter-item "><a href="../http/modify/headers.html"><strong aria-hidden="true">10.8.4.</strong> Customize headers</a></li><li class="chapter-item "><a href="../http/modify/referer.html"><strong aria-hidden="true">10.8.5.</strong> Referer</a></li><li class="chapter-item "><a href="../http/modify/user-agent.html"><strong aria-hidden="true">10.8.6.</strong> User-agent</a></li><li class="chapter-item "><a href="../http/modify/ranges.html"><strong aria-hidden="true">10.8.7.</strong> Ranges</a></li><li class="chapter-item "><a href="../http/modify/conditionals.html"><strong aria-hidden="true">10.8.8.</strong> Conditionals</a></li><li class="chapter-item "><a href="../http/modify/compression.html"><strong aria-hidden="true">10.8.9.</strong> Compression</a></li></ol></li><li class="chapter-item "><a href="../http/cookies/index.html"><strong aria-hidden="true">10.9.</strong> Cookies</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../http/cookies/engine.html"><strong aria-hidden="true">10.9.1.</strong> Cookie engine</a></li><li class="chapter-item "><a href="../http/cookies/reading.html"><strong aria-hidden="true">10.9.2.</strong> Reading cookies from file</a></li><li class="chapter-item "><a href="../http/cookies/writing.html"><strong aria-hidden="true">10.9.3.</strong> Writing cookies to file</a></li><li class="chapter-item "><a href="../http/cookies/newsession.html"><strong aria-hidden="true">10.9.4.</strong> New cookie session</a></li><li class="chapter-item "><a href="../http/cookies/fileformat.html"><strong aria-hidden="true">10.9.5.</strong> Cookie file format</a></li></ol></li><li class="chapter-item "><a href="../http/https.html"><strong aria-hidden="true">10.10.</strong> HTTPS</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../http/https/hsts.html"><strong aria-hidden="true">10.10.1.</strong> HSTS</a></li><li class="chapter-item "><a href="../http/https/altsvc.html"><strong aria-hidden="true">10.10.2.</strong> Alternative Services</a></li></ol></li><li class="chapter-item "><a href="../http/browserlike.html"><strong aria-hidden="true">10.11.</strong> Scripting browser-like tasks</a></li></ol></li><li class="chapter-item "><a href="../ftp/index.html"><strong aria-hidden="true">11.</strong> Command line FTP</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../ftp/dirlist.html"><strong aria-hidden="true">11.1.</strong> FTP Directory listing</a></li><li class="chapter-item "><a href="../ftp/upload.html"><strong aria-hidden="true">11.2.</strong> Uploading with FTP</a></li><li class="chapter-item "><a href="../ftp/cmds.html"><strong aria-hidden="true">11.3.</strong> Custom FTP commands</a></li><li class="chapter-item "><a href="../ftp/twoconnections.html"><strong aria-hidden="true">11.4.</strong> Two connections</a></li><li class="chapter-item "><a href="../ftp/traversedir.html"><strong aria-hidden="true">11.5.</strong> Directory traversing</a></li><li class="chapter-item "><a href="../ftp/ftps.html"><strong aria-hidden="true">11.6.</strong> FTPS</a></li></ol></li><li class="chapter-item "><a href="../libcurl/index.html"><strong aria-hidden="true">12.</strong> libcurl</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../libcurl/headers.html"><strong aria-hidden="true">12.1.</strong> Header files</a></li><li class="chapter-item "><a href="../libcurl/globalinit.html"><strong aria-hidden="true">12.2.</strong> Global initialization</a></li><li class="chapter-item "><a href="../libcurl/api.html"><strong aria-hidden="true">12.3.</strong> API compatibility</a></li><li class="chapter-item "><a href="../libcurl/--libcurl.html"><strong aria-hidden="true">12.4.</strong> --libcurl</a></li><li class="chapter-item "><a href="../libcurl/threading.html"><strong aria-hidden="true">12.5.</strong> multi-threading</a></li><li class="chapter-item "><a href="../libcurl/curlcode.html"><strong aria-hidden="true">12.6.</strong> CURLcode return codes</a></li><li class="chapter-item "><a href="../libcurl/verbose.html"><strong aria-hidden="true">12.7.</strong> Verbose operations</a></li><li class="chapter-item "><a href="../libcurl/caches.html"><strong aria-hidden="true">12.8.</strong> Caches</a></li><li class="chapter-item "><a href="../libcurl/performance.html"><strong aria-hidden="true">12.9.</strong> Performance</a></li><li class="chapter-item "><a href="../libcurl/cplusplus.html"><strong aria-hidden="true">12.10.</strong> for C++ programmers</a></li></ol></li><li class="chapter-item "><a href="../transfers/index.html"><strong aria-hidden="true">13.</strong> libcurl transfers</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../transfers/easyhandle.html"><strong aria-hidden="true">13.1.</strong> Easy handle</a></li><li class="chapter-item "><a href="../transfers/options/index.html"><strong aria-hidden="true">13.2.</strong> curl easy options</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../transfers/options/num.html"><strong aria-hidden="true">13.2.1.</strong> Set numerical options</a></li><li class="chapter-item "><a href="../transfers/options/strings.html"><strong aria-hidden="true">13.2.2.</strong> Set string options</a></li><li class="chapter-item "><a href="../transfers/options/tls.html"><strong aria-hidden="true">13.2.3.</strong> TLS options</a></li><li class="chapter-item "><a href="../transfers/options/all.html"><strong aria-hidden="true">13.2.4.</strong> All options</a></li><li class="chapter-item "><a href="../transfers/options/info.html"><strong aria-hidden="true">13.2.5.</strong> Get option information</a></li></ol></li><li class="chapter-item "><a href="../transfers/drive/index.html"><strong aria-hidden="true">13.3.</strong> Drive transfers</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../transfers/drive/easy.html"><strong aria-hidden="true">13.3.1.</strong> Drive with easy</a></li><li class="chapter-item "><a href="../transfers/drive/multi.html"><strong aria-hidden="true">13.3.2.</strong> Drive with multi</a></li><li class="chapter-item "><a href="../transfers/drive/multi-socket.html"><strong aria-hidden="true">13.3.3.</strong> Drive with multi_socket</a></li></ol></li><li class="chapter-item "><a href="../transfers/callbacks/index.html"><strong aria-hidden="true">13.4.</strong> Callbacks</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../transfers/callbacks/write.html"><strong aria-hidden="true">13.4.1.</strong> Write data</a></li><li class="chapter-item "><a href="../transfers/callbacks/read.html"><strong aria-hidden="true">13.4.2.</strong> Read data</a></li><li class="chapter-item "><a href="../transfers/callbacks/progress.html"><strong aria-hidden="true">13.4.3.</strong> Progress information</a></li><li class="chapter-item "><a href="../transfers/callbacks/header.html"><strong aria-hidden="true">13.4.4.</strong> Header data</a></li><li class="chapter-item "><a href="../transfers/callbacks/debug.html"><strong aria-hidden="true">13.4.5.</strong> Debug</a></li><li class="chapter-item "><a href="../transfers/callbacks/sockopt.html"><strong aria-hidden="true">13.4.6.</strong> sockopt</a></li><li class="chapter-item "><a href="../transfers/callbacks/sslcontext.html"><strong aria-hidden="true">13.4.7.</strong> SSL context</a></li><li class="chapter-item "><a href="../transfers/callbacks/seek.html"><strong aria-hidden="true">13.4.8.</strong> Seek and ioctl</a></li><li class="chapter-item "><a href="../transfers/callbacks/conversions.html"><strong aria-hidden="true">13.4.9.</strong> Network data conversion</a></li><li class="chapter-item "><a href="../transfers/callbacks/openclosesocket.html"><strong aria-hidden="true">13.4.10.</strong> Opensocket and closesocket</a></li><li class="chapter-item "><a href="../transfers/callbacks/sshkey.html"><strong aria-hidden="true">13.4.11.</strong> SSH key</a></li><li class="chapter-item "><a href="../transfers/callbacks/rtsp.html"><strong aria-hidden="true">13.4.12.</strong> RTSP interleaved data</a></li><li class="chapter-item "><a href="../transfers/callbacks/ftpmatch.html"><strong aria-hidden="true">13.4.13.</strong> FTP wildcard matching</a></li><li class="chapter-item "><a href="../transfers/callbacks/resolver.html"><strong aria-hidden="true">13.4.14.</strong> Resolver start</a></li><li class="chapter-item "><a href="../transfers/callbacks/trailers.html"><strong aria-hidden="true">13.4.15.</strong> Sending trailers</a></li><li class="chapter-item "><a href="../transfers/callbacks/hsts.html"><strong aria-hidden="true">13.4.16.</strong> HSTS</a></li><li class="chapter-item "><a href="../transfers/callbacks/prereq.html"><strong aria-hidden="true">13.4.17.</strong> Prereq</a></li></ol></li><li class="chapter-item "><a href="../transfers/conn/index.html"><strong aria-hidden="true">13.5.</strong> Connection control</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../transfers/conn/how.html"><strong aria-hidden="true">13.5.1.</strong> How libcurl connects</a></li><li class="chapter-item "><a href="../transfers/conn/local.html"><strong aria-hidden="true">13.5.2.</strong> Local address and port number</a></li><li class="chapter-item "><a href="../transfers/conn/reuse.html"><strong aria-hidden="true">13.5.3.</strong> Connection reuse</a></li><li class="chapter-item "><a href="../transfers/conn/keepalive.html"><strong aria-hidden="true">13.5.4.</strong> Keep alive</a></li><li class="chapter-item "><a href="../transfers/conn/names.html"><strong aria-hidden="true">13.5.5.</strong> Name resolving</a></li><li class="chapter-item "><a href="../transfers/conn/proxies.html"><strong aria-hidden="true">13.5.6.</strong> Proxies</a></li></ol></li><li class="chapter-item "><a href="../transfers/control/index.html"><strong aria-hidden="true">13.6.</strong> Transfer control</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../transfers/control/stop.html"><strong aria-hidden="true">13.6.1.</strong> Stop</a></li><li class="chapter-item "><a href="../transfers/control/stopslow.html"><strong aria-hidden="true">13.6.2.</strong> Stop slow transfers</a></li><li class="chapter-item "><a href="../transfers/control/ratelimit.html"><strong aria-hidden="true">13.6.3.</strong> Rate limit</a></li><li class="chapter-item "><a href="../transfers/control/meter.html"><strong aria-hidden="true">13.6.4.</strong> Progress meter</a></li><li class="chapter-item "><a href="../transfers/control/progress-callback.html"><strong aria-hidden="true">13.6.5.</strong> Progress callback</a></li></ol></li><li class="chapter-item "><a href="../transfers/auth.html"><strong aria-hidden="true">13.7.</strong> Authentication</a></li><li class="chapter-item "><a href="../transfers/cleanup.html"><strong aria-hidden="true">13.8.</strong> Cleanup</a></li><li class="chapter-item "><a href="../transfers/getinfo.html"><strong aria-hidden="true">13.9.</strong> Post transfer info</a></li></ol></li><li class="chapter-item "><a href="../libcurl-http/index.html"><strong aria-hidden="true">14.</strong> libcurl HTTP</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../libcurl-http/responses.html"><strong aria-hidden="true">14.1.</strong> Responses</a></li><li class="chapter-item "><a href="../libcurl-http/requests.html"><strong aria-hidden="true">14.2.</strong> Requests</a></li><li class="chapter-item "><a href="../libcurl-http/versions.html"><strong aria-hidden="true">14.3.</strong> Versions</a></li><li class="chapter-item "><a href="../libcurl-http/ranges.html"><strong aria-hidden="true">14.4.</strong> Ranges</a></li><li class="chapter-item "><a href="../libcurl-http/auth.html"><strong aria-hidden="true">14.5.</strong> Authentication</a></li><li class="chapter-item "><a href="../libcurl-http/cookies.html"><strong aria-hidden="true">14.6.</strong> Cookies</a></li><li class="chapter-item "><a href="../libcurl-http/download.html"><strong aria-hidden="true">14.7.</strong> Download</a></li><li class="chapter-item "><a href="../libcurl-http/upload.html"><strong aria-hidden="true">14.8.</strong> Upload</a></li><li class="chapter-item "><a href="../libcurl-http/multiplexing.html"><strong aria-hidden="true">14.9.</strong> Multiplexing</a></li><li class="chapter-item "><a href="../libcurl-http/hsts.html"><strong aria-hidden="true">14.10.</strong> HSTS</a></li><li class="chapter-item "><a href="../libcurl-http/alt-svc.html"><strong aria-hidden="true">14.11.</strong> alt-svc</a></li></ol></li><li class="chapter-item "><a href="../helpers/index.html"><strong aria-hidden="true">15.</strong> libcurl helpers</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../helpers/sharing.html"><strong aria-hidden="true">15.1.</strong> Share data between handles</a></li><li class="chapter-item "><a href="../helpers/url/index.html"><strong aria-hidden="true">15.2.</strong> URL API</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../helpers/url/include.html"><strong aria-hidden="true">15.2.1.</strong> Include files</a></li><li class="chapter-item "><a href="../helpers/url/init.html"><strong aria-hidden="true">15.2.2.</strong> Create, cleanup, duplicate</a></li><li class="chapter-item "><a href="../helpers/url/parse.html"><strong aria-hidden="true">15.2.3.</strong> Parse a URL</a></li><li class="chapter-item "><a href="../helpers/url/redirect.html"><strong aria-hidden="true">15.2.4.</strong> Redirect to URL</a></li><li class="chapter-item "><a href="../helpers/url/get.html"><strong aria-hidden="true">15.2.5.</strong> Get a URL</a></li><li class="chapter-item "><a href="../helpers/url/get-part.html"><strong aria-hidden="true">15.2.6.</strong> Get URL parts</a></li><li class="chapter-item "><a href="../helpers/url/set-part.html"><strong aria-hidden="true">15.2.7.</strong> Set URL parts</a></li><li class="chapter-item "><a href="../helpers/url/append-query.html"><strong aria-hidden="true">15.2.8.</strong> Append to the query</a></li><li class="chapter-item "><a href="../helpers/url/setopt.html"><strong aria-hidden="true">15.2.9.</strong> CURLOPT_CURLU</a></li></ol></li><li class="chapter-item "><a href="../helpers/ws/index.html"><strong aria-hidden="true">15.3.</strong> WebSocket</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../helpers/ws/support.html"><strong aria-hidden="true">15.3.1.</strong> Support</a></li><li class="chapter-item "><a href="../helpers/ws/urls.html"><strong aria-hidden="true">15.3.2.</strong> URLs</a></li><li class="chapter-item "><a href="../helpers/ws/concept.html"><strong aria-hidden="true">15.3.3.</strong> Concept</a></li><li class="chapter-item "><a href="../helpers/ws/options.html"><strong aria-hidden="true">15.3.4.</strong> Options</a></li><li class="chapter-item "><a href="../helpers/ws/read.html"><strong aria-hidden="true">15.3.5.</strong> Read</a></li><li class="chapter-item "><a href="../helpers/ws/meta.html"><strong aria-hidden="true">15.3.6.</strong> Meta</a></li><li class="chapter-item "><a href="../helpers/ws/write.html"><strong aria-hidden="true">15.3.7.</strong> Write</a></li></ol></li><li class="chapter-item "><a href="../helpers/headerapi/index.html"><strong aria-hidden="true">15.4.</strong> Headers API</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../helpers/headerapi/struct.html"><strong aria-hidden="true">15.4.1.</strong> Header struct</a></li><li class="chapter-item "><a href="../helpers/headerapi/get.html"><strong aria-hidden="true">15.4.2.</strong> Get a header</a></li><li class="chapter-item "><a href="../helpers/headerapi/iterate.html"><strong aria-hidden="true">15.4.3.</strong> Iterate over headers</a></li></ol></li></ol></li><li class="chapter-item "><a href="../examples/index.html"><strong aria-hidden="true">16.</strong> libcurl examples</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../examples/get.html"><strong aria-hidden="true">16.1.</strong> Get a simple HTTP page</a></li><li class="chapter-item "><a href="../examples/getinmem.html"><strong aria-hidden="true">16.2.</strong> Get a response into memory</a></li><li class="chapter-item "><a href="../examples/login.html"><strong aria-hidden="true">16.3.</strong> Submit a login form over HTTP</a></li><li class="chapter-item "><a href="../examples/ftplist.html"><strong aria-hidden="true">16.4.</strong> Get an FTP directory listing</a></li><li class="chapter-item "><a href="../examples/http-ul-nonblock.html"><strong aria-hidden="true">16.5.</strong> Non-blocking HTTP form-post</a></li></ol></li><li class="chapter-item "><a href="../bindings/index.html"><strong aria-hidden="true">17.</strong> libcurl bindings</a></li><li class="chapter-item "><a href="../internals/index.html"><strong aria-hidden="true">18.</strong> libcurl internals</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../internals/easy.html"><strong aria-hidden="true">18.1.</strong> Easy handles and connections</a></li><li class="chapter-item "><a href="../internals/multi.html"><strong aria-hidden="true">18.2.</strong> Everything is multi</a></li><li class="chapter-item "><a href="../internals/statemachines.html"><strong aria-hidden="true">18.3.</strong> State machines</a></li><li class="chapter-item "><a href="../internals/handler.html"><strong aria-hidden="true">18.4.</strong> Protocol handler</a></li><li class="chapter-item "><a href="../internals/backends.html"><strong aria-hidden="true">18.5.</strong> Backends</a></li><li class="chapter-item "><a href="../internals/caches.html"><strong aria-hidden="true">18.6.</strong> Caches and state</a></li><li class="chapter-item "><a href="../internals/timeouts.html"><strong aria-hidden="true">18.7.</strong> Timeouts</a></li><li class="chapter-item "><a href="../internals/windows-vs-unix.html"><strong aria-hidden="true">18.8.</strong> Windows vs Unix</a></li><li class="chapter-item "><a href="../internals/memory-debugging.html"><strong aria-hidden="true">18.9.</strong> Memory debugging</a></li><li class="chapter-item "><a href="../internals/content-encoding.html"><strong aria-hidden="true">18.10.</strong> Content Encoding</a></li><li class="chapter-item "><a href="../internals/structs.html"><strong aria-hidden="true">18.11.</strong> Structs</a></li><li class="chapter-item "><a href="../internals/resolving.html"><strong aria-hidden="true">18.12.</strong> Resolving hostnames</a></li><li class="chapter-item "><a href="../internals/tests/index.html"><strong aria-hidden="true">18.13.</strong> Tests</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../internals/tests/file-format.html"><strong aria-hidden="true">18.13.1.</strong> Test file format</a></li><li class="chapter-item "><a href="../internals/tests/build.html"><strong aria-hidden="true">18.13.2.</strong> Build tests</a></li><li class="chapter-item "><a href="../internals/tests/run.html"><strong aria-hidden="true">18.13.3.</strong> Run tests</a></li><li class="chapter-item "><a href="../internals/tests/debug.html"><strong aria-hidden="true">18.13.4.</strong> Debug builds</a></li><li class="chapter-item "><a href="../internals/tests/servers.html"><strong aria-hidden="true">18.13.5.</strong> Test servers</a></li><li class="chapter-item "><a href="../internals/tests/curl.html"><strong aria-hidden="true">18.13.6.</strong> curl tests</a></li><li class="chapter-item "><a href="../internals/tests/libcurl.html"><strong aria-hidden="true">18.13.7.</strong> libcurl tests</a></li><li class="chapter-item "><a href="../internals/tests/unit.html"><strong aria-hidden="true">18.13.8.</strong> Unit tests</a></li><li class="chapter-item "><a href="../internals/tests/valgrind.html"><strong aria-hidden="true">18.13.9.</strong> Valgrind</a></li><li class="chapter-item "><a href="../internals/tests/ci.html"><strong aria-hidden="true">18.13.10.</strong> Continuous Integration</a></li><li class="chapter-item "><a href="../internals/tests/autobuilds.html"><strong aria-hidden="true">18.13.11.</strong> Autobuilds</a></li><li class="chapter-item "><a href="../internals/tests/torture.html"><strong aria-hidden="true">18.13.12.</strong> Torture</a></li></ol></li></ol></li><li class="chapter-item "><a href="../bookindex.html"><strong aria-hidden="true">19.</strong> Index</a></li></ol> </div> <div id="sidebar-resize-handle" class="sidebar-resize-handle"> <div class="sidebar-resize-indicator"></div> </div> </nav>  <script> var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox'); sidebarScrollbox.addEventListener('click', function(e) { if (e.target.tagName === 'A') { sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop); } }, { passive: true }); var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll'); sessionStorage.removeItem('sidebar-scroll'); if (sidebarScrollTop) { // preserve sidebar scroll position when navigating via links within 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(Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> <i class="fa fa-search"></i> </button> </div> <h1 class="menu-title">everything curl</h1> <div class="right-buttons"> <a href="../print.html" title="Print this book" aria-label="Print this book"> <i id="print-button" class="fa fa-print"></i> </a> </div> </div> <div id="search-wrapper" class="hidden"> <form id="searchbar-outer" class="searchbar-outer"> <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> </form> <div id="searchresults-outer" class="searchresults-outer hidden"> <div id="searchresults-header" class="searchresults-header"></div> <ul id="searchresults"> </ul> </div> </div>  <script> document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); }); </script> <div id="content" class="content"> <main> <h1 id="protocols"><a class="header" href="#protocols">Protocols</a></h1> <p>The language used to ask for data to get sent—in either direction—is called <strong>the protocol</strong>. The protocol describes exactly how to ask the server for data, or to tell the server that there is data coming.</p> <p>Protocols are typically defined by the IETF (<a href="https://www.ietf.org/">Internet Engineering Task Force</a>), which hosts RFC documents that describe exactly how each protocol works: how clients and servers are supposed to act and what to send and so on.</p> <h2 id="what-protocols-does-curl-support"><a class="header" href="#what-protocols-does-curl-support">What protocols does curl support?</a></h2> <p>curl supports protocols that allow data transfers in either or both directions. We usually also restrict ourselves to protocols which have a URI format described in an RFC or at least is somewhat widely used, as curl works primarily with URLs (URIs really) as the input key that specifies the transfer.</p> <p>The latest curl (as of this writing) supports these protocols:</p> <p>DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS, WSS</p> <p>To complicate matters further, the protocols often exist in different versions or flavors as well.</p> <h2 id="what-other-protocols-are-there"><a class="header" href="#what-other-protocols-are-there">What other protocols are there?</a></h2> <p>The world is full of protocols, both old and new. Old protocols get abandoned and dropped and new ones get introduced. There is never a state of stability but the situation changes from day to day and year to year. You can rest assured that there will be new protocols added in the list above in the future and that there will be new versions of the protocols already listed.</p> <p>There are, of course, already other protocols in existence that curl does not yet support. We are open to supporting more protocols that suit the general curl paradigms, we just need developers to write the necessary code adjustments for them.</p> <h2 id="how-are-protocols-developed"><a class="header" href="#how-are-protocols-developed">How are protocols developed?</a></h2> <p>Both new versions of existing protocols and entirely new protocols are usually developed by persons or teams that feel that the existing ones are not good enough. Something about them makes them not suitable for a particular use case or perhaps some new idea has popped up that could be applied to improve things.</p> <p>Of course, nothing prevents anyone from developing a protocol entirely on their own at their own pleasure in their own backyard, but the major protocols are usually brought to the IETF at a fairly early stage where they are then discussed, refined, debated and polished and then eventually, ideally, turned into a published RFC document.</p> <p>Software developers then read the RFC specifications and deploy their code in the world based on their interpretations of the words in those documents. It sometimes turns out that some of the specifications are subject to vastly different interpretations or sometimes the engineers are just lazy and ignore sound advice in the specs and deploy something that does not adhere. Writing software that interoperates with other implementations of the specifications can therefore end up being hard work.</p> <h2 id="how-much-do-protocols-change"><a class="header" href="#how-much-do-protocols-change">How much do protocols change?</a></h2> <p>Like software, protocol specifications are frequently updated and new protocol versions are created.</p> <p>Most protocols allow some level of extensibility which makes new extensions show up over time, extensions that make sense to support.</p> <p>The interpretation of a protocol sometimes changes even if the spec remains the same.</p> <p>The protocols mentioned in this chapter are all <em>Application Protocols</em>, which means they are transferred over more lower level protocols, like TCP, UDP and TLS. They are also themselves protocols that change over time, get new features and get attacked so that new ways of handling security, etc., forces curl to adapt and change.</p> <h2 id="about-adhering-to-standards-and-who-is-right"><a class="header" href="#about-adhering-to-standards-and-who-is-right">About adhering to standards and who is right</a></h2> <p>Generally, there are protocol specs that tell us how to send and receive data for specific protocols. The protocol specs we follow are RFCs put together and published by IETF.</p> <p>Some protocols are not properly documented in a final RFC, like, for example, SFTP for which our implementation is based on an Internet-draft that is not even the last available one.</p> <p>Protocols are, however, spoken by two parties and like in any given conversation, there are then two sides of understanding something or interpreting the given instructions in a spec. Also, lots of network software is written without the authors paying close attention to the spec so they end up taking some shortcuts, or perhaps they just interpreted the text differently. Sometimes even mistakes and bugs make software behave in ways that are not mandated by the spec and sometimes even downright forbidden in the specs.</p> <p>In the curl project we use the published specs as rules on how to act until we learn anything else. If popular alternative implementations act differently than what we think the spec says and that alternative behavior is what works widely on the big Internet, then chances are we change foot and instead decide to act like those others. If a server refuses to talk with us when we think we follow the spec but works fine when we bend the rules ever so slightly, then we probably end up bending them exactly that way—if we can still work successfully with other implementations.</p> <p>Ultimately, it is a personal decision and up for discussion in every case where we think a spec and the real world do not align.</p> <p>In the worst cases we introduce options to let application developers and curl users have the final say on what curl should do. I say worst because it is often really tough to ask users to make these decisions as it usually involves tricky details and weirdness going on and it is a lot to ask of users. We should always do our best to avoid pushing such protocol decisions to users.</p> </main> <nav class="nav-wrapper" aria-label="Page navigation">  <a rel="prev" href="../protocols/network.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next prefetch" href="../protocols/curl.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> <div style="clear: both"></div> </nav> </div> </div> <nav class="nav-wide-wrapper" aria-label="Page navigation"> <a rel="prev" href="../protocols/network.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next prefetch" href="../protocols/curl.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> </nav> </div> <script> window.playground_copyable = true; </script> <script src="../elasticlunr.min.js"></script> <script src="../mark.min.js"></script> <script src="../searcher.js"></script> <script src="../clipboard.min.js"></script> <script src="../highlight.js"></script> <script src="../book.js"></script>  </div> </body> </html>