Server-Side Java - Java - page 653

os . close ();

}

} catch catch ( IOException e ) {

System . err . println ( e );

}

}

}

Handling Multiple Clients

Problem

Your server needs to handle multiple clients.

Solution

Use a thread for each.

Discussion

In the C world, several mechanisms allow a server to handle multiple clients. One is to use a
special “system call” select() or poll() , which notifies the server when any of a set of
file/socket descriptors is ready to read, ready to write, or has an error. By including its ren-
dezvous socket (equivalent to our ServerSocket ) in this list, the C-based server can read
from any of a number of clients in any order. Java does not provide this call, because it is not
readily implementable on some Java platforms. Instead, Java uses the general-purpose
Thread mechanism, as described in Program: Threaded Network Server . Threads are, in fact,
one of the other mechanisms available to the C programmer on most platforms. Each time
the code accepts a new connection from the ServerSocket , it immediately constructs and
starts a new thread object to process that client. [ 50 ]

The Java code to implement accepting on a socket is pretty simple, apart from having to
catch IOException s:

/** Run the main loop of the Server. */
void runServer( ) {
while (true) {