Java Programming

One of my assignments was to create a serial I/O device simulator. I've found bits and pieces of code that should work correctly, but for some reason I'm getting a connection refused exception. Here is the while error:

java.net.ConnectException: Connection refused
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
        at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
        at java.net.Socket.connect(Socket.java:519)
        at java.net.Socket.connect(Socket.java:469)
        at java.net.Socket.<init>(Socket.java:366)
        at java.net.Socket.<init>(Socket.java:179)
        at Driver.connect(Driver.java:20)
        at SocketUser.run(SocketUser.java:33)

Line 20 of Driver.java is:

            socket = new Socket("localhost", 54321);

Line 33 of SocketUser.java is:

connect();

I could post the entire code, but its 6 files big. I tried using a different port, but I still get the error.