Summary

TCP_KEEPIDLE, TCP_KEEPCOUNT, and TCP_KEEPINTERVAL are non-standard socket options supported on several platforms to provide fine control over the TCP/IP keep alive mechanism. It should be possible to set these socket options via the setOption method defined by java.net.Socket and java.nio.channels.SocketChannel.

Problem

When the SO_KEEPALIVE option is enabled, TCP probes a connection that has been idle for some amount of time. The default value for this idle period is 2 hours which is too long for most applications. The TCP_KEEPIDLE, TCP_KEEPCOUNT, TCP_KEEPINTERVAL option can be used to affect this value for a given socket.

Solution

Add a JDK-specific socket option that supports setting TCP_KEEPIDLE, TCP_KEEPCOUNT, TCP_KEEPINTERVAL, on platforms that support it. The option can be set/get through the existing set/getOption methods on Socket and NetworkChannel.

Specification

To jdk.net.ExtendedSocketOptions, add the following new socket options:

<pre> <code> /** * Keep-Alive idle time. * * The value of this socket option is an {@code Integer} that is the number * of seconds of idle time before keep-alive initiates a probe. The socket * option is specific to stream-oriented sockets using the TCP/IP protocol. * The exact semantics of this socket option are system dependent. * * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been * idle for some amount of time. The default value for this idle period is * system dependent, but is typically 2 hours. The {@code TCP_KEEPIDLE} * option can be used to affect this value for a given socket. */ public static final SocketOption<Integer> TCP_KEEPIDLE = new ExtSocketOption<Integer>("TCP_KEEPIDLE", Integer.class); /** * Keep-Alive retransmission interval time. * * The value of this socket option is an {@code Integer} that is the number * of seconds to wait before retransmitting a keep-alive probe. The socket * option is specific to stream-oriented sockets using the TCP/IP protocol. * The exact semantics of this socket option are system dependent. * * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been * idle for some amount of time. If the remote system does not respond to a * keep-alive probe, TCP retransmits the probe after some amount of time. * The default value for this retransmission interval is system dependent, * but is typically 75 seconds. The {@code TCP_KEEPINTERVAL} option can be * used to affect this value for a given socket. */ public static final SocketOption<Integer> TCP_KEEPINTERVAL = new ExtSocketOption<Integer>("TCP_KEEPINTERVAL", Integer.class); /** * Keep-Alive retransmission maximum limit. * * The value of this socket option is an {@code Integer} that is the maximum * number of keep-alive probes to be sent. The socket option is specific to * stream-oriented sockets using the TCP/IP protocol. The exact semantics of * this socket option are system dependent. * * When the {@link java.net.StandardSocketOptions#SO_KEEPALIVE * SO_KEEPALIVE} option is enabled, TCP probes a connection that has been * idle for some amount of time. If the remote system does not respond to a * keep-alive probe, TCP retransmits the probe a certain number of times * before a connection is considered to be broken. The default value for * this keep-alive probe retransmit limit is system dependent, but is * typically 8. The {@code TCP_KEEPCOUNT} option can be used to affect this * value for a given socket. */ public static final SocketOption<Integer> TCP_KEEPCOUNT = new ExtSocketOption<Integer>("TCP_KEEPCOUNT", Integer.class); </code> </pre>