1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE manualpage SYSTEM "./style/manualpage.dtd">
3 <?xml-stylesheet type="text/xsl" href="./style/manual.en.xsl"?>
4 <!-- $LastChangedRevision$ -->
7 Licensed to the Apache Software Foundation (ASF) under one or more
8 contributor license agreements. See the NOTICE file distributed with
9 this work for additional information regarding copyright ownership.
10 The ASF licenses this file to You under the Apache License, Version 2.0
11 (the "License"); you may not use this file except in compliance with
12 the License. You may obtain a copy of the License at
14 http://www.apache.org/licenses/LICENSE-2.0
16 Unless required by applicable law or agreed to in writing, software
17 distributed under the License is distributed on an "AS IS" BASIS,
18 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
19 See the License for the specific language governing permissions and
20 limitations under the License.
23 <manualpage metafile="bind.xml.meta">
25 <title>Binding to Addresses and Ports</title>
28 <p>Configuring Apache HTTP Server to listen on specific addresses and ports.</p>
31 <seealso><a href="vhosts/">Virtual Hosts</a></seealso>
32 <seealso><a href="dns-caveats.html">DNS Issues</a></seealso>
34 <section id="overview">
35 <title>Overview</title>
40 <module>mpm_common</module>
43 <directive module="core" type="section">VirtualHost</directive>
44 <directive module="mpm_common">Listen</directive>
49 <p>When httpd starts, it binds to some port and address on
50 the local machine and waits for incoming requests. By default,
51 it listens to all addresses on the machine. However, it may need to
52 be told to listen on specific ports, or only on selected
53 addresses, or a combination of both. This is often combined with the
54 <a href="vhosts/">Virtual Host</a> feature, which determines how
55 <code>httpd</code> responds to different IP addresses, hostnames and
58 <p>The <directive module="mpm_common">Listen</directive>
59 directive tells the server to accept
60 incoming requests only on the specified port(s) or
61 address-and-port combinations. If only a port number is
62 specified in the <directive module="mpm_common">Listen</directive>
63 directive, the server listens to the given port on all interfaces.
64 If an IP address is given as well as a port, the server will listen
65 on the given port and interface. Multiple <directive
66 module="mpm_common">Listen</directive> directives may be used to
67 specify a number of addresses and ports to listen on. The
68 server will respond to requests from any of the listed
69 addresses and ports.</p>
71 <p>For example, to make the server accept connections on both
72 port 80 and port 8000, on all interfaces, use:</p>
75 <highlight language="config">
81 <p>To make the server accept connections on port 80 for one interface,
82 and port 8000 on another, use</p>
85 <highlight language="config">
91 <p>IPv6 addresses must be enclosed in square brackets, as in the
92 following example:</p>
95 <highlight language="config">
96 Listen [2001:db8::a00:20ff:fea7:ccea]:80
100 <note type="warning"><p>Overlapping <directive
101 module="mpm_common">Listen</directive> directives will result in a
102 fatal error which will prevent the server from starting up.</p>
105 (48)Address already in use: make_sock: could not bind to address [::]:80
109 href="http://wiki.apache.org/httpd/CouldNotBindToAddress">the
110 discussion in the wiki</a> for further troubleshooting tips.</p>
117 <title>Special IPv6 Considerations</title>
119 <p>A growing number of platforms implement IPv6, and
120 <glossary>APR</glossary> supports IPv6 on most of these platforms,
121 allowing httpd to allocate IPv6 sockets, and to handle requests sent
124 <p>One complicating factor for httpd administrators is whether or
125 not an IPv6 socket can handle both IPv4 connections and IPv6
126 connections. Handling IPv4 connections with an IPv6 socket uses
127 IPv4-mapped IPv6 addresses, which are allowed by default on most
128 platforms, but are disallowed by default on FreeBSD, NetBSD, and
129 OpenBSD, in order to match the system-wide policy on those
130 platforms. On systems where it is disallowed by default, a
131 special <program>configure</program> parameter can change this behavior
134 <p>On the other hand, on some platforms, such as Linux and Tru64, the
135 <strong>only</strong> way to handle both IPv6 and IPv4 is to use
136 mapped addresses. If you want <code>httpd</code> to handle IPv4 and IPv6 connections
137 with a minimum of sockets, which requires using IPv4-mapped IPv6
138 addresses, specify the <code>--enable-v4-mapped</code> <program>
139 configure</program> option.</p>
141 <p><code>--enable-v4-mapped</code> is the default on all platforms except
142 FreeBSD, NetBSD, and OpenBSD, so this is probably how your httpd was
145 <p>If you want httpd to handle IPv4 connections only, regardless of
146 what your platform and APR will support, specify an IPv4 address on all
147 <directive module="mpm_common">Listen</directive> directives, as in the
148 following examples:</p>
151 <highlight language="config">
157 <p>If your platform supports it and you want httpd to handle IPv4 and
158 IPv6 connections on separate sockets (i.e., to disable IPv4-mapped
159 addresses), specify the <code>--disable-v4-mapped</code> <program>
160 configure</program> option. <code>--disable-v4-mapped</code> is the
161 default on FreeBSD, NetBSD, and OpenBSD.</p>
164 <section id="protocol">
165 <title>Specifying the protocol with Listen</title>
166 <p>The optional second <var>protocol</var> argument of
167 <directive module="mpm_common">Listen</directive>
168 is not required for most
169 configurations. If not specified, <code>https</code> is the default for
170 port 443 and <code>http</code> the default for all other ports. The
171 protocol is used to determine which module should handle a request, and
172 to apply protocol specific optimizations with the
173 <directive module="core">AcceptFilter</directive> directive.</p>
175 <p>You only need to set the protocol if you are running on non-standard
176 ports. For example, running an <code>https</code> site on port 8443:</p>
179 <highlight language="config">
180 Listen 192.170.2.1:8443 https
185 <section id="virtualhost">
186 <title>How This Works With Virtual Hosts</title>
189 module="mpm_common">Listen</directive> directive does not implement
190 Virtual Hosts - it only tells the
191 main server what addresses and ports to listen on. If no
192 <directive module="core" type="section">VirtualHost</directive>
193 directives are used, the server will behave
194 in the same way for all accepted requests. However,
195 <directive module="core" type="section">VirtualHost</directive>
196 can be used to specify a different behavior
197 for one or more of the addresses or ports. To implement a
198 VirtualHost, the server must first be told to listen to the
199 address and port to be used. Then a
200 <directive module="core" type="section">VirtualHost</directive> section
201 should be created for the specified address and port to set the
202 behavior of this virtual host. Note that if the
203 <directive module="core" type="section">VirtualHost</directive>
204 is set for an address and port that the
205 server is not listening to, it cannot be accessed.</p>