curl/docs/libcurl/opts/CURLMOPT_MAX_HOST_CONNECTIONS.3

.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at https://curl.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" * SPDX-License-Identifier: curl
.\" *
.\" **************************************************************************
.\"
.TH CURLMOPT_MAX_HOST_CONNECTIONS 3 "17 Jun 2014" libcurl libcurl
.SH NAME
CURLMOPT_MAX_HOST_CONNECTIONS \- max number of connections to a single host
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_MAX_HOST_CONNECTIONS,
                            long max);
.fi
.SH DESCRIPTION
Pass a long to indicate \fBmax\fP. The set number will be used as the maximum
amount of simultaneously open connections to a single host (a host being the
same as a host name + port number pair). For each new session to a host,
libcurl will open a new connection up to the limit set by
\fICURLMOPT_MAX_HOST_CONNECTIONS(3)\fP. When the limit is reached, the
sessions will be pending until a connection becomes available. If
\fICURLMOPT_PIPELINING(3)\fP is enabled, libcurl will try to pipeline if the
host is capable of it.

The default \fBmax\fP value is 0, unlimited.  However, for backwards
compatibility, setting it to 0 when \fICURLMOPT_PIPELINING(3)\fP is 1 will not
be treated as unlimited. Instead it will open only 1 connection and try to
pipeline on it.

This set limit is also used for proxy connections, and then the proxy is
considered to be the host for which this limit counts.

When more transfers are added to the multi handle than what can be performed
due to the set limit, they will be queued up waiting for their chance. When
that happens, the \fICURLOPT_TIMEOUT_MS(3)\fP timeout will be counted
inclusive of the waiting time, meaning that if you set a too narrow timeout in
such a case the transfer might never even start before it times out.

Even in the queued up situation, the \fICURLOPT_CONNECTTIMEOUT_MS(3)\fP
timeout is however treated as a per-connect timeout.
.SH DEFAULT
0
.SH PROTOCOLS
HTTP(S)
.SH EXAMPLE
.nf
CURLM *m = curl_multi_init();
/* do no more than 2 connections per host */
curl_multi_setopt(m, CURLMOPT_MAX_HOST_CONNECTIONS, 2L);
.fi
.SH AVAILABILITY
Added in 7.30.0
.SH RETURN VALUE
Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLMOPT_MAXCONNECTS "(3), " CURLMOPT_MAX_TOTAL_CONNECTIONS "(3), "