Presents your 
JAVA E-NEWSLETTER for March 3, 2003

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USE TIMEOUTS WHEN READING SOCKETS

Although Java 1.4 introduced non-blocking I/O to the Java API, Java
versions 1.3 and earlier don't support the feature. However, you can use
the timeout property of the java.net.Socket class to get something like
non-blocking I/O.

To use the timeout property, you first create the socket, then set the
timeout you want. The setSoTimeout method takes one parameter, an int that
specifies the number of milliseconds the timeout socket should wait
before throwing an exception, like this:

Socket s = new Socket(server, port);
System.out.println(s.getSoTimeout());
s.setSoTimeout(5000);
InputStream in = s.getInputStream();

Now attempt to read from the socket. If no data can be read within the
specified timeout, a java.io.InterruptedIOException will be thrown. You
can catch the exception and decide whether to attempt another read:

try {
   while ( (bytesRead = in.read(buffer)) != -1 ) {
      // do something with the data
      System.out.println(new String(buffer, 0, bytesRead));
   }
}
catch (InterruptedIOException e) {
   System.err.print("timeout on read");
   // decide whether to keep on reading or not
}

In Java versions prior to 1.4, your applications may have to block when
reading from sockets, but they don't have to stand still.

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