Java Network Programming, Second Edition

Some Useful Servers

This section shows several servers you can build with server sockets. It starts with a server you can use to test client responses and requests, much as you use Telnet to test server behavior. Then we present three different HTTP servers, each with a different special purpose and each slightly more complex than the previous one.

Client Tester

In the previous chapter, you learned how to use Telnet to experiment with servers. There’s no equivalent program to test clients, so let’s create one. Example 11.5 is a program called ClientTester that runs on a port specified on thecommand-line, shows all data sent by the client, and allows you to send a response to the client by typing it on the command line. For example, you can use this program to see the commands that Netscape Navigator sends to a server.

Note

Clients are rarely as forgiving about unexpected server responses as servers are about unexpected client responses. If at all possible, try to run the clients that connect to this program on a Unix system or some other platform that is moderately crash-proof. Don’t run them on a Mac or Windows 98, which are less stable.

This program uses two threads: one to handle input from the client and the other to send output from the server. Using two threads allows the program to handle input and output simultaneously: it can be sending a response to the client while receiving a request—or, more to the point, it can send data to the client while waiting for the client to respond. ...