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Editorial Team
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Asked: 2026-05-23T11:44:49+00:00

I’m trying to write a server and client program in java. I’ve not done

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I’m trying to write a server and client program in java. I’ve not done this before, so I figured I’ld start with the examples provided at the links below.

Server code:
http://java.sun.com/developer/onlineTraining/Programming/BasicJava2/Code/SocketServer.java

Client code:
http://java.sun.com/developer/onlineTraining/Programming/BasicJava2/Code/SocketClient.java

I made a few changes in terms of the naming, but the basic functionality should be the same. The server app runs fine, but the client app is throwing an UnknownHostException. I thought the problem was probably something to do with the IP address used in both apps not being valid. I’m running this on Mac, and I don’t claim to be an expert on IP addresses, but I figured it might be a good idea to write code that would actually print out the IP address, which is posted below, in case it’s at all helpful.

java.net.InetAddress address = java.net.InetAddress.getLocalHost();
System.out.println("IP Address  :"+address.getHostAddress());

However, this code returns some number like 463.827.201.789(not really this but just for demonstrative purposes), which definitely doesn’t work as a parameter of the Socket constructor I’m using.

Anyway, I don’t know what the issue is and I need help here.

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1 Answer

  1. Editorial Team

    Printing the InetAddress objects getHostAddress() method prints a textual representation of the address (as specified in the API, check http://download.oracle.com/javase/6/docs/api/java/net/InetAddress.html#getHostAddress()). This should be the IP address of your computer? (Or possible 127.0.0.1, the address that always points to your local computer).

    The Socket class (http://download.oracle.com/javase/6/docs/api/java/net/Socket.html) takes an InetAddress + port number in the constructor so you should be able to pass it the InetAddress and the first parameter and the port number that your SocketServer listens on. (Each server socket opens up a listener on a port number which you can basically choose yourself, check http://download.oracle.com/javase/6/docs/api/java/net/ServerSocket.html).

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