Client/server with sockets - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 464

If the client successfully connects to the server, it spins off the socket to an
instance of the Thread subclass DataClientWorker ,which handles commu-
nications with the server. After the connection is made, the text on the “ Start „
button becomes “ Stop „ .Ifthe user clicks on the “ Stop „ button, the stop()
method is invoked, via the actionPerformed() method, and this tells the
DataClientWorker to break the connection and die.
When the DataClientWorker receives data from the server, it calls back
to the DataClient via the setData (int[] data) method to pass the
data on. This method uses the pack() method in the Histogram class (see
Section 6.11) to display the values in the array for the top histogram in the user
interface. For the data channel (i.e. the data array index) given in the interface
text field, the distribution of values are displayed in the second histogram.
15.7 The DataClientWorker
As we indicated in Figure 15.1, communication with the server is mostly han-
dled by the DataClientWorker object. This Thread subclass first opens the
streams to the server and then carries out a simple log-in procedure with the
server by passing the user name to it. See the doConnection() and login()
methods in the code snippet shown below. Note that, as with DataServer , the
class holds some utility methods for the I/O operations.
... In the class DataClientWorker ....
/** Remain in a loop to monitor the I/O from the server.
* Display the data.
**/
public void run () {
// The socket connection was made by the caller, now
// set up the streams and do a login
try {
if (!doConnection ()) {
fDataClient.println (" Connection/login failed");
return;
}
}
catch (IOException ioe) {
fDataClient.println (" I/O exception with serve:" +
ioe);
}
int num - channels = -1;