Sockets for Clients - Java Network Programming - page 261

SO_LINGER
public void setSoLinger ( boolean on , int seconds ) throws SocketException
public int getSoLinger () throws SocketException
The SO_LINGER option specifies what to do with datagrams that have not yet been
sent when a socket is closed. By default, the close() method returns immediately; but
the system still tries to send any remaining data. If the linger time is set to zero, any
unsent packets are thrown away when the socket is closed. If SO_LINGER is turned on
and the linger time is any positive value, the close() method blocks while waiting the
specified number of seconds for the data to be sent and the acknowledgments to be
received. When that number of seconds has passed, the socket is closed and any re‐
maining data is not sent, acknowledgment or no.
These two methods each throw a SocketException if the underlying socket imple‐
mentation does not support the SO_LINGER option. The setSoLinger() method can
also throw an IllegalArgumentException if you try to set the linger time to a negative
value. However, the getSoLinger() method may return -1 to indicate that this option
is disabled, and as much time as is needed is taken to deliver the remaining data; for
example, to set the linger timeout for the Socket s to four minutes, if it's not already
set to some other value:
if ( s . getTcpSoLinger () == - 1 ) s . setSoLinger ( true , 240 );
The maximum linger time is 65,535 seconds, and may be smaller on some platforms.
Times larger than that will be reduced to the maximum linger time. Frankly, 65,535
seconds (more than 18 hours) is much longer than you actually want to wait. Generally,
the platform default value is more appropriate.
SO_TIMEOUT
public void setSoTimeout ( int milliseconds ) throws SocketException
public int getSoTimeout () throws SocketException
Normally when you try to read data from a socket, the read() call blocks as long as
necessary to get enough bytes. By setting SO_TIMEOUT, you ensure that the call will
not block for more than a fixed number of milliseconds. When the timeout expires, an
InterruptedIOException is thrown, and you should be prepared to catch it. However,
the socket is still connected. Although this read() call failed, you can try to read from
the socket again. The next call may succeed.
Timeouts are given in milliseconds. Zero is interpreted as an infinite timeout; it is the
default value. For example, to set the timeout value of the Socket object s to 3 minutes
if it isn't already set, specify 180,000 milliseconds:
if ( s . getSoTimeout () == 0 ) s . setSoTimeout ( 180000 );