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10 <title>Binding to Addresses and Ports - Apache HTTP Server Version 2.5</title>
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20 <p class="apache">Apache HTTP Server Version 2.5</p>
21 <img alt="" src="./images/feather.png" /></div>
22 <div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div>
24 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.5</a></div><div id="page-content"><div id="preamble"><h1>Binding to Addresses and Ports</h1>
26 <p><span>Available Languages: </span><a href="./de/bind.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |
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35 <p>Configuring Apache HTTP Server to listen on specific addresses and ports.</p>
37 <div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#overview">Overview</a></li>
38 <li><img alt="" src="./images/down.gif" /> <a href="#reload">Changing Listen configuration on restart</a></li>
39 <li><img alt="" src="./images/down.gif" /> <a href="#ipv6">Special IPv6 Considerations</a></li>
40 <li><img alt="" src="./images/down.gif" /> <a href="#protocol">Specifying the protocol with Listen</a></li>
41 <li><img alt="" src="./images/down.gif" /> <a href="#virtualhost">How This Works With Virtual Hosts</a></li>
42 </ul><h3>See also</h3><ul class="seealso"><li><a href="vhosts/">Virtual Hosts</a></li><li><a href="dns-caveats.html">DNS Issues</a></li><li><a href="#comments_section">Comments</a></li></ul></div>
43 <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
45 <h2><a name="overview" id="overview">Overview</a> <a title="Permanent link" href="#overview" class="permalink">¶</a></h2>
48 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/core.html">core</a></code></li><li><code class="module"><a href="./mod/mpm_common.html">mpm_common</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code></li><li><code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code></li></ul></td></tr></table>
51 <p>When httpd starts, it binds to some port and address on
52 the local machine and waits for incoming requests. By default,
53 it listens to all addresses on the machine. However, it may need to
54 be told to listen on specific ports, or only on selected
55 addresses, or a combination of both. This is often combined with the
56 <a href="vhosts/">Virtual Host</a> feature, which determines how
57 <code>httpd</code> responds to different IP addresses, hostnames and
60 <p>The <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code>
61 directive tells the server to accept
62 incoming requests only on the specified port(s) or
63 address-and-port combinations. If only a port number is
64 specified in the <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code>
65 directive, the server listens to the given port on all interfaces.
66 If an IP address is given as well as a port, the server will listen
67 on the given port and interface. Multiple <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code> directives may be used to
68 specify a number of addresses and ports to listen on. The
69 server will respond to requests from any of the listed
70 addresses and ports.</p>
72 <p>For example, to make the server accept connections on both
73 port 80 and port 8000, on all interfaces, use:</p>
75 <div class="example"><pre class="prettyprint lang-config">Listen 80
79 <p>To make the server accept connections on port 80 for one interface,
80 and port 8000 on another, use</p>
82 <div class="example"><pre class="prettyprint lang-config">Listen 192.0.2.1:80
83 Listen 192.0.2.5:8000</pre>
86 <p>IPv6 addresses must be enclosed in square brackets, as in the
87 following example:</p>
89 <div class="example"><pre class="prettyprint lang-config">Listen [2001:db8::a00:20ff:fea7:ccea]:80</pre>
92 <div class="warning"><p>Overlapping <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code> directives will result in a
93 fatal error which will prevent the server from starting up.</p>
95 <div class="example"><p><code>
96 (48)Address already in use: make_sock: could not bind to address [::]:80
99 <p>See <a href="http://wiki.apache.org/httpd/CouldNotBindToAddress">the
100 discussion in the wiki</a> for further troubleshooting tips.</p>
104 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
105 <div class="section">
106 <h2><a name="reload" id="reload">Changing Listen configuration on restart</a> <a title="Permanent link" href="#reload" class="permalink">¶</a></h2>
109 <p>When httpd is restarted, special consideration must be made for
110 changes to <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code> directives. During a restart, httpd keeps ports
111 bound (as in the original configuration) to avoid generating
112 "Connection refused" errors for any new attempts to connect to the
113 server. If changes are made to the set of <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code> directives used
114 which conflict with the old configuration, configuration will fail
115 and the server will terminate.</p>
117 <p>For example, changing from configuration:</p>
119 <div class="example"><pre class="prettyprint lang-config">Listen 127.0.0.1:80</pre>
122 <p>to the following may fail, because binding to port 80 across
123 all addresses conflicts with binding to port 80 on just
126 <div class="example"><pre class="prettyprint lang-config">Listen 80</pre>
129 <p>To have such configuration changes take effect, it is necessary
130 to stop and then start the server.</p>
132 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
133 <div class="section">
134 <h2><a name="ipv6" id="ipv6">Special IPv6 Considerations</a> <a title="Permanent link" href="#ipv6" class="permalink">¶</a></h2>
137 <p>A growing number of platforms implement IPv6, and
138 <a class="glossarylink" href="./glossary.html#apr" title="see glossary">APR</a> supports IPv6 on most of these platforms,
139 allowing httpd to allocate IPv6 sockets, and to handle requests sent
142 <p>One complicating factor for httpd administrators is whether or
143 not an IPv6 socket can handle both IPv4 connections and IPv6
144 connections. Handling IPv4 connections with an IPv6 socket uses
145 IPv4-mapped IPv6 addresses, which are allowed by default on most
146 platforms, but are disallowed by default on FreeBSD, NetBSD, and
147 OpenBSD, in order to match the system-wide policy on those
148 platforms. On systems where it is disallowed by default, a
149 special <code class="program"><a href="./programs/configure.html">configure</a></code> parameter can change this behavior
152 <p>On the other hand, on some platforms, such as Linux and Tru64, the
153 <strong>only</strong> way to handle both IPv6 and IPv4 is to use
154 mapped addresses. If you want <code>httpd</code> to handle IPv4 and IPv6 connections
155 with a minimum of sockets, which requires using IPv4-mapped IPv6
156 addresses, specify the <code>--enable-v4-mapped</code> <code class="program"><a href="./programs/configure.html">configure</a></code> option.</p>
158 <p><code>--enable-v4-mapped</code> is the default on all platforms except
159 FreeBSD, NetBSD, and OpenBSD, so this is probably how your httpd was
162 <p>If you want httpd to handle IPv4 connections only, regardless of
163 what your platform and APR will support, specify an IPv4 address on all
164 <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code> directives, as in the
165 following examples:</p>
167 <div class="example"><pre class="prettyprint lang-config">Listen 0.0.0.0:80
168 Listen 192.0.2.1:80</pre>
171 <p>If your platform supports it and you want httpd to handle IPv4 and
172 IPv6 connections on separate sockets (i.e., to disable IPv4-mapped
173 addresses), specify the <code>--disable-v4-mapped</code> <code class="program"><a href="./programs/configure.html">configure</a></code> option. <code>--disable-v4-mapped</code> is the
174 default on FreeBSD, NetBSD, and OpenBSD.</p>
175 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
176 <div class="section">
177 <h2><a name="protocol" id="protocol">Specifying the protocol with Listen</a> <a title="Permanent link" href="#protocol" class="permalink">¶</a></h2>
179 <p>The optional second <var>protocol</var> argument of
180 <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code>
181 is not required for most
182 configurations. If not specified, <code>https</code> is the default for
183 port 443 and <code>http</code> the default for all other ports. The
184 protocol is used to determine which module should handle a request, and
185 to apply protocol specific optimizations with the
186 <code class="directive"><a href="./mod/core.html#acceptfilter">AcceptFilter</a></code> directive.</p>
188 <p>You only need to set the protocol if you are running on non-standard
189 ports. For example, running an <code>https</code> site on port 8443:</p>
191 <div class="example"><pre class="prettyprint lang-config">Listen 192.170.2.1:8443 https</pre>
193 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
194 <div class="section">
195 <h2><a name="virtualhost" id="virtualhost">How This Works With Virtual Hosts</a> <a title="Permanent link" href="#virtualhost" class="permalink">¶</a></h2>
198 <p> The <code class="directive"><a href="./mod/mpm_common.html#listen">Listen</a></code> directive does not implement
199 Virtual Hosts - it only tells the
200 main server what addresses and ports to listen on. If no
201 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
202 directives are used, the server will behave
203 in the same way for all accepted requests. However,
204 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
205 can be used to specify a different behavior
206 for one or more of the addresses or ports. To implement a
207 VirtualHost, the server must first be told to listen to the
208 address and port to be used. Then a
209 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code> section
210 should be created for the specified address and port to set the
211 behavior of this virtual host. Note that if the
212 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
213 is set for an address and port that the
214 server is not listening to, it cannot be accessed.</p>
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