Simple Client Server communication

Question

I am learning currently about client server communication using Java through sockets. First of all I retrieve my own machine's IP Address using following code.

InetAddress ownIP=InetAddress.getLocalHost(); //the result being 192.168.56.1

Now I write the simple client server application using the above mentioned address as follow

public class SimpleClientServer { public static void main(String[] args) { //sending "Hello World" to the server Socket clientSocket = null; PrintWriter out = null; BufferedReader in = null; try { clientSocket = new Socket("192.168.56.1", 16000); out = new PrintWriter(clientSocket.getOutputStream(), true); in = new BufferedReader(new InputStreamReader( clientSocket.getInputStream())); out.println("Hello World"); out.close(); in.close(); clientSocket.close(); } catch(IOException e) { System.err.println("Error occured " + e); } } }

The result hower reads a follow.

Error occured java.net.ConnectException: Connection refused: connect

What is the reason for this. Is it just the wrong host address?

First setup a server socket at port 16000 on the same machine, and then run the same code — Johnydep
– Johnydep, Commented Feb 6, 2012 at 11:35
1) Please tell us the line where the error occur 2) Please show the server code. — Adel Boutros
– Adel Boutros, Commented Feb 6, 2012 at 11:36

Christopher Hackett · Accepted Answer · 2012-02-06 11:32:17Z

From the code you have given you seem to suggest that there is currently nothing listening on port 16000 for the socket to connect to.

If this is the case you need to implement something like

ServerSocket serverSocket = null; try { serverSocket = new ServerSocket(16000); } catch (IOException e) { System.err.println("Could not listen on port: 16000."); System.exit(1); }

More information can be found in the Java online documentation and a full example is included.

Simon Germain · Accepted Answer · 2012-02-06 11:32:52Z

2

With sockets, no matter what language you're using, you either initiate a connection with socket_connect or you listen and accept with socket_listen and socket_accept. Your socket_connect call is trying to connect to an ip address that doesn't seem to be listening to anything.

answered Feb 6, 2012 at 11:32

Simon Germain

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3 Comments

Chris Dennett Over a year ago

I'm afraid that the Socket constructor does the connection in this case. On the other end, a ServerSocket is needed, which you would invoke the accept() method upon to receive a Socket endpoint.

Simon Germain Over a year ago

I was just trying to illustrate the functionality.

Chris Dennett Over a year ago

I just saw the last bit of your answer (oops) ;) You're correct.

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