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src/java.base/share/classes/java/net/doc-files/net-properties.html
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<TITLE>Networking Properties</TITLE>
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! <H1 ALIGN=CENTER>Networking Properties</H1>
! <P ALIGN=LEFT>There are a few standard system properties used to
alter the mechanisms and behavior of the various classes of the
java.net package. Some are checked only once at startup of the VM,
and therefore are best set using the -D option of the java command,
while others have a more dynamic nature and can also be changed using
the <a href="../../lang/System.html#setProperty(java.lang.String,%20java.lang.String)">System.setProperty()</a> API.
The purpose of this document is to list
and detail all of these properties.</P>
<P>If there is no special note, a property value is checked every time it is used.</P>
! <a name="Ipv4IPv6"></a>
<H2>IPv4 / IPv6</H2>
<UL>
<LI><P><B>java.net.preferIPv4Stack</B> (default: false)<BR>
If IPv6 is available on the operating system the
underlying native socket will be, by default, an IPv6 socket which
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Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
or visit www.oracle.com if you need additional information or have any
questions.
-->
<HTML>
<HEAD>
<META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=iso-8859-1">
<TITLE>Networking Properties</TITLE>
</HEAD>
<BODY LANG="en-US" DIR="LTR">
! <H1 style="text-align:center">Networking Properties</H1>
! <P>There are a few standard system properties used to
alter the mechanisms and behavior of the various classes of the
java.net package. Some are checked only once at startup of the VM,
and therefore are best set using the -D option of the java command,
while others have a more dynamic nature and can also be changed using
the <a href="../../lang/System.html#setProperty(java.lang.String,%20java.lang.String)">System.setProperty()</a> API.
The purpose of this document is to list
and detail all of these properties.</P>
<P>If there is no special note, a property value is checked every time it is used.</P>
! <a id="Ipv4IPv6"></a>
<H2>IPv4 / IPv6</H2>
<UL>
<LI><P><B>java.net.preferIPv4Stack</B> (default: false)<BR>
If IPv6 is available on the operating system the
underlying native socket will be, by default, an IPv6 socket which
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change that preference and use IPv6 addresses over IPv4 ones where
possible, or <B>system</B> to preserve the order of the addresses as
returned by the operating system.</P>
</UL>
<P>Both of these properties are checked only once, at startup.</P>
! <a name="Proxies"></a>
<H2>Proxies</H2>
<P>A proxy server allows indirect connection to network services and
is used mainly for security (to get through firewalls) and
performance reasons (proxies often do provide caching mechanisms).
The following properties allow for configuration of the various type
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change that preference and use IPv6 addresses over IPv4 ones where
possible, or <B>system</B> to preserve the order of the addresses as
returned by the operating system.</P>
</UL>
<P>Both of these properties are checked only once, at startup.</P>
! <a id="Proxies"></a>
<H2>Proxies</H2>
<P>A proxy server allows indirect connection to network services and
is used mainly for security (to get through firewalls) and
performance reasons (proxies often do provide caching mechanisms).
The following properties allow for configuration of the various type
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tell the java.net stack, setting this property to <B>true</B>, to use
the system proxy settings (both these systems let you set proxies
globally through their user interface). Note that this property is
checked only once at startup.</P>
</UL>
! <a name="MiscHTTP"></a>
<H2>Misc HTTP properties</H2>
<UL>
<LI><P><B>http.agent</B> (default: “Java/<version>”)<BR>
Defines the string sent in the User-Agent request header in http
requests. Note that the string “Java/<version>” will
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tell the java.net stack, setting this property to <B>true</B>, to use
the system proxy settings (both these systems let you set proxies
globally through their user interface). Note that this property is
checked only once at startup.</P>
</UL>
! <a id="MiscHTTP"></a>
<H2>Misc HTTP properties</H2>
<UL>
<LI><P><B>http.agent</B> (default: “Java/<version>”)<BR>
Defines the string sent in the User-Agent request header in http
requests. Note that the string “Java/<version>” will
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property is defined, then its value will be used a the domain
name.</P>
</OL>
</UL>
<P>All these properties are checked only once at startup.</P>
! <a name="AddressCache"></a>
<H2>Address Cache</H2>
<P>The java.net package, when doing name resolution, uses an address
cache for both security and performance reasons. Any address
resolution attempt, be it forward (name to IP address) or reverse (IP
address to name), will have its result cached, whether it was
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property is defined, then its value will be used a the domain
name.</P>
</OL>
</UL>
<P>All these properties are checked only once at startup.</P>
! <a id="AddressCache"></a>
<H2>Address Cache</H2>
<P>The java.net package, when doing name resolution, uses an address
cache for both security and performance reasons. Any address
resolution attempt, be it forward (name to IP address) or reverse (IP
address to name), will have its result cached, whether it was
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