1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE manualpage SYSTEM "./style/manualpage.dtd">
<?xml-stylesheet type="text/xsl" href="./style/manual.en.xsl"?>
<!-- $LastChangedRevision$ -->
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<manualpage metafile="bind.xml.meta">
<title>Binding</title>
<summary>
<p>Configuring Apache HTTP Server to listen on specific addresses and ports.</p>
</summary>
<seealso><a href="vhosts/">Virtual Hosts</a></seealso>
<seealso><a href="dns-caveats.html">DNS Issues</a></seealso>
<section id="overview">
<title>Overview</title>
<related>
<modulelist>
<module>core</module>
<module>mpm_common</module>
</modulelist>
<directivelist>
<directive module="core" type="section">VirtualHost</directive>
<directive module="mpm_common">Listen</directive>
</directivelist>
</related>
<p>When httpd starts, it binds to some port and address on
the local machine and waits for incoming requests. By default,
it listens to all addresses on the machine. However, it may need to
be told to listen on specific ports, or only on selected
addresses, or a combination of both. This is often combined with the
Virtual Host feature, which determines how httpd responds to
different IP addresses, hostnames and ports.</p>
<p>The <directive module="mpm_common">Listen</directive>
directive tells the server to accept
incoming requests only on the specified ports or
address-and-port combinations. If only a port number is
specified in the <directive module="mpm_common">Listen</directive>
directive, the server
listens to the given port on all interfaces. If an IP address
is given as well as a port, the server will listen on the given
port and interface. Multiple <directive
module="mpm_common">Listen</directive> directives may be used to
specify a number of addresses and ports to listen on. The
server will respond to requests from any of the listed
addresses and ports.</p>
<p>For example, to make the server accept connections on both
port 80 and port 8000, on all interfaces, use:</p>
<example>
Listen 80<br />
Listen 8000
</example>
<p>To make the server accept connections on port 80 for one interface,
and port 8000 on another, use</p>
<example>
Listen 192.0.2.1:80<br />
Listen 192.0.2.5:8000
</example>
<p>IPv6 addresses must be enclosed in square brackets, as in the
following example:</p>
<example>
Listen [2001:db8::a00:20ff:fea7:ccea]:80
</example>
</section>
<section id="ipv6">
<title>Special IPv6 Considerations</title>
<p>A growing number of platforms implement IPv6, and
<glossary>APR</glossary> supports IPv6 on most of these platforms,
allowing httpd to allocate IPv6 sockets, and to handle requests sent
over IPv6.</p>
<p>One complicating factor for httpd administrators is whether or
not an IPv6 socket can handle both IPv4 connections and IPv6
connections. Handling IPv4 connections with an IPv6 socket uses
IPv4-mapped IPv6 addresses, which are allowed by default on most
platforms, but are disallowed by default on FreeBSD, NetBSD, and
OpenBSD, in order to match the system-wide policy on those
platforms. On systems where it is disallowed by default, a
special <program>configure</program> parameter can change this behavior
for httpd.</p>
<p>On the other hand, on some platforms, such as Linux and Tru64, the
<strong>only</strong> way to handle both IPv6 and IPv4 is to use
mapped addresses. If you want httpd to handle IPv4 and IPv6 connections
with a minimum of sockets, which requires using IPv4-mapped IPv6
addresses, specify the <code>--enable-v4-mapped</code> <program>
configure</program> option.</p>
<p><code>--enable-v4-mapped</code> is the default on all platforms except
FreeBSD, NetBSD, and OpenBSD, so this is probably how your httpd was
built.</p>
<p>If you want httpd to handle IPv4 connections only, regardless of
what your platform and APR will support, specify an IPv4 address on all
<directive module="mpm_common">Listen</directive> directives, as in the
following examples:</p>
<example>
Listen 0.0.0.0:80<br />
Listen 192.0.2.1:80
</example>
<p>If your platform supports it and you want httpd to handle IPv4 and
IPv6 connections on separate sockets (i.e., to disable IPv4-mapped
addresses), specify the <code>--disable-v4-mapped</code> <program>
configure</program> option. <code>--disable-v4-mapped</code> is the
default on FreeBSD, NetBSD, and OpenBSD.</p>
</section>
<section id="virtualhost">
<title>How This Works With Virtual Hosts</title>
<p> The <directive
module="mpm_common">Listen</directive> directive does not implement
Virtual Hosts - it only tells the
main server what addresses and ports to listen on. If no
<directive module="core" type="section">VirtualHost</directive>
directives are used, the server will behave
in the same way for all accepted requests. However,
<directive module="core" type="section">VirtualHost</directive>
can be used to specify a different behavior
for one or more of the addresses or ports. To implement a
VirtualHost, the server must first be told to listen to the
address and port to be used. Then a
<directive module="core" type="section">VirtualHost</directive> section
should be created for the specified address and port to set the
behavior of this virtual host. Note that if the
<directive module="core" type="section">VirtualHost</directive>
is set for an address and port that the
server is not listening to, it cannot be accessed.</p>
</section>
</manualpage>
|
