Setting TCP parameters for Socket?

[markspace]

Sahm's post reminded me about this:

Investigating Socket::isReachable() a while back, I discovered that the
Socket constructor actually establishes a TCP connection. This means
you can't set TCP parameters for the inital connection. For example,
SO_TIMEOUT.

Socket sock = new Socket( hostname, port );
sock.setSoTimeout( 6000 ); // too late!

There's no way that I can see to change the time out of the initial
connection, which occurs in the first line above, in the constructor.
You can set the time out for subsequent reads, but not the first connect.

Does anyone know of a way to control various TCP parameters, esp. the
time out, for the Socket constructor?

 

[markspace]

To partially answer my own question here, it appears that the initial
connection in the Socket constructor is sensitive to Thread.interrupt().
This strikes me as a somewhat hokey solution however. I'm still
hoping for something better.



private static void test2( String hostname, int port ) {
Thread t = new Thread( new ConnectTask( hostname, port ) );
try {
Thread.sleep( 1000 );
} catch(InterruptedException ex) {}
t.interrupt();
while( t.isAlive() ) {
try {
t.join();
} catch (InterruptedException ex ) {}
}
System.out.println("Thread finished. " + t );
}



private static class ConnectTask implements Runnable {
private final String hostname;
private final int port;

public ConnectTask(String hostname, int port) {
this.hostname = hostname;
this.port = port;
}

@Override
public void run() {
try {
Socket sock = new Socket( hostname, port );
System.out.println("created: "+sock);
} catch (IOException ex) {
System.err.println(ex);
throw new RuntimeException(ex);
}
}

}

 

[markspace]

private static void test2( String hostname, int port ) {
Thread t = new Thread( new ConnectTask( hostname, port ) );

t.start(); // *cough*

try {
Thread.sleep( 1000 );

Nope, like a dofus, I forgot to start the thread. Do that, and the
connect doesn't interrupt. No worky.

 

[Steven Simpson]

Socket sock = new Socket( hostname, port );
sock.setSoTimeout( 6000 ); // too late!

There's no way that I can see to change the time out of the initial
connection, which occurs in the first line above, in the constructor.
You can set the time out for subsequent reads, but not the first connect.

Is anything stopping you from created an unconnected Socket, then
calling connect() on it, with the timeout specified as an argument?

You could also try setSoTimeout() between the constructor and connect(),
but it appears to be for reads, not necessarily connects. Of course,
that might be the only way for other socket options.

 

[Daniele Futtorovic]

Sahm's post reminded me about this:

Investigating Socket::isReachable() a while back, I discovered that the
Socket constructor actually establishes a TCP connection. This means
you can't set TCP parameters for the inital connection. For example,
SO_TIMEOUT.

Socket sock = new Socket( hostname, port );
sock.setSoTimeout( 6000 ); // too late!

There's no way that I can see to change the time out of the initial
connection, which occurs in the first line above, in the constructor.
You can set the time out for subsequent reads, but not the first connect.

Does anyone know of a way to control various TCP parameters, esp. the
time out, for the Socket constructor?

<http://download.oracle.com/javase/6/docs/api/java/net/Socket.html>

Socket(InetAddress address, int port)
Creates a stream socket *and connects it* to the specified port number
at the specified IP address.

Socket()
Creates an *unconnected socket*, with the system-default type of
SocketImpl.

 

[markspace]

Socket()
Creates an *unconnected socket*, with the system-default type of
SocketImpl.

Doh. Thanks guys.