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src/java.base/share/classes/java/net/doc-files/net-properties.html

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  6  This code is free software; you can redistribute it and/or modify it
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 14  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 15  version 2 for more details (a copy is included in the LICENSE file that
 16  accompanied this code).
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 18  You should have received a copy of the GNU General Public License version
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 44 <a id="Ipv4IPv6"></a>
 45 <H2>IPv4 / IPv6</H2>
 46 <UL>
 47 	<LI><P><B>{@systemProperty java.net.preferIPv4Stack}</B> (default: false)<BR>
 48 	If IPv6 is available on the operating system the
 49 	underlying native socket will be, by default, an IPv6 socket which
 50 	lets applications connect to, and accept connections from, both
 51 	IPv4 and IPv6 hosts. However, in the case an application would
 52 	rather use IPv4 only sockets, then this property can be set to <B>true</B>.
 53 	The implication is that it will not be possible for the application
 54 	to communicate with IPv6 only hosts.</P>
 55 	<LI><P><B>{@systemProperty java.net.preferIPv6Addresses}</B> (default: false)<BR>
 56 	When dealing with a host which has both IPv4
 57 	and IPv6 addresses, and if IPv6 is available on the operating
 58 	system, the default behavior is to prefer using IPv4 addresses over
 59 	IPv6 ones. This is to ensure backward compatibility: for example,
 60 	for applications that depend on the representation of an IPv4 address
 61 	(e.g. 192.168.1.1). This property can be set to <B>true</B> to
 62 	change that preference and use IPv6 addresses over IPv4 ones where
 63 	possible, or <B>system</B> to preserve the order of the addresses as
 64     returned by the operating system.</P>
 65 </UL>
 66 <P>Both of these properties are checked only once, at startup.</P>
 67 <a id="Proxies"></a>
 68 <H2>Proxies</H2>
 69 <P>A proxy server allows indirect connection to network services and
 70 is used mainly for security (to get through firewalls) and
 71 performance reasons (proxies often do provide caching mechanisms).
 72 The following properties allow for configuration of the various type
 73 of proxies.</P>
 74 <UL>
 75 	<LI><P>HTTP</P>
 76 	<P>The following proxy settings are used by the HTTP protocol handler.</P>
 77 	<UL>
 78 		<LI><P><B>{@systemProperty http.proxyHost}</B> (default: &lt;none&gt;)<BR>
 79 	        The hostname, or address, of the proxy server.
 80 		</P>
 81 		<LI><P><B>{@systemProperty http.proxyPort}</B> (default: {@code 80})<BR>
 82 	        The port number of the proxy server.</P>
 83 		<LI><P><B>{@systemProperty http.nonProxyHosts}</B> (default: {@code localhost|127.*|[::1]})<BR>
 84 	        Indicates the hosts that should be accessed without going

  1 <!DOCTYPE HTML>
  2 <!--
  3  Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved.
  4  DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  5 
  6  This code is free software; you can redistribute it and/or modify it
  7  under the terms of the GNU General Public License version 2 only, as
  8  published by the Free Software Foundation.  Oracle designates this
  9  particular file as subject to the "Classpath" exception as provided
 10  by Oracle in the LICENSE file that accompanied this code.
 11 
 12  This code is distributed in the hope that it will be useful, but WITHOUT
 13  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 14  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 15  version 2 for more details (a copy is included in the LICENSE file that
 16  accompanied this code).
 17 
 18  You should have received a copy of the GNU General Public License version
 19  2 along with this work; if not, write to the Free Software Foundation,
 20  Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 21 
 22  Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 23  or visit www.oracle.com if you need additional information or have any

 44 <a id="Ipv4IPv6"></a>
 45 <H2>IPv4 / IPv6</H2>
 46 <UL>
 47 	<LI><P><B>{@systemProperty java.net.preferIPv4Stack}</B> (default: false)<BR>
 48 	If IPv6 is available on the operating system the
 49 	underlying native socket will be, by default, an IPv6 socket which
 50 	lets applications connect to, and accept connections from, both
 51 	IPv4 and IPv6 hosts. However, in the case an application would
 52 	rather use IPv4 only sockets, then this property can be set to <B>true</B>.
 53 	The implication is that it will not be possible for the application
 54 	to communicate with IPv6 only hosts.</P>
 55 	<LI><P><B>{@systemProperty java.net.preferIPv6Addresses}</B> (default: false)<BR>
 56 	When dealing with a host which has both IPv4
 57 	and IPv6 addresses, and if IPv6 is available on the operating
 58 	system, the default behavior is to prefer using IPv4 addresses over
 59 	IPv6 ones. This is to ensure backward compatibility: for example,
 60 	for applications that depend on the representation of an IPv4 address
 61 	(e.g. 192.168.1.1). This property can be set to <B>true</B> to
 62 	change that preference and use IPv6 addresses over IPv4 ones where
 63 	possible, or <B>system</B> to preserve the order of the addresses as
 64     returned by the system-wide {@linkplain java.net.spi.InetAddressResolver resolver}.</P>
 65 </UL>
 66 <P>Both of these properties are checked only once, at startup.</P>
 67 <a id="Proxies"></a>
 68 <H2>Proxies</H2>
 69 <P>A proxy server allows indirect connection to network services and
 70 is used mainly for security (to get through firewalls) and
 71 performance reasons (proxies often do provide caching mechanisms).
 72 The following properties allow for configuration of the various type
 73 of proxies.</P>
 74 <UL>
 75 	<LI><P>HTTP</P>
 76 	<P>The following proxy settings are used by the HTTP protocol handler.</P>
 77 	<UL>
 78 		<LI><P><B>{@systemProperty http.proxyHost}</B> (default: &lt;none&gt;)<BR>
 79 	        The hostname, or address, of the proxy server.
 80 		</P>
 81 		<LI><P><B>{@systemProperty http.proxyPort}</B> (default: {@code 80})<BR>
 82 	        The port number of the proxy server.</P>
 83 		<LI><P><B>{@systemProperty http.nonProxyHosts}</B> (default: {@code localhost|127.*|[::1]})<BR>
 84 	        Indicates the hosts that should be accessed without going
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