— Scott McNealy, Sun Microsystems Chairman, President and ceo

Can there ever be more than 
one program running on a single 
port? In other words, can two 
applications on the same server have 
the same port number?
A: 
No! If you try to bind a program 
to a port that is already in use, you’ll 
get a BindException. To bind a program 
to a port just means starting up a 
server application and telling it to run 
on a particular port. Again, you’ll learn 
more about this when we get to the 
server part of this chapter.

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478
 
chapter 15
To communicate over a Socket connection, you use streams. 
Regular old I/O streams, just like we used in the last chapter. One 
of the coolest features in Java is that most of your I/O work won’t 
care what your high-level chain stream is actually connected to. In 
other words, you can use a BufferedReader just like you did when 
you were writing to a file, the difference is that the underlying 
connection stream is connected to a Socket rather than a File!
To read data from a Socket, use a 
BufferedReader
Socket chatSocket = new Socket(“127.0.0.1”, 5000);
127.0.0.1 is the IP address for “localhost”, in 
other words, the one this code is running on. You 
can use this when you’re testing your client and 
server on a single, stand-alone machine.
1
Make a Socket connection to the server
BufferedReader reader = new BufferedReader(stream);
String message = reader.readLine();
3
Make a BufferedReader and read!
Chain the BufferedReader to the 
InputStreamReader(which was chained to the low-
level connection stream we got from the Socket.)
The port number, which you know 
because we TOLD you that 5000 is 
the port number for our chat server.