Java Programming

why when i close a client i get java.net.SocketException:

java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at sun.nio.cs.StreamDecoder.readBytes(Unknown Source)
at sun.nio.cs.StreamDecoder.implRead(Unknown Source)
at sun.nio.cs.StreamDecoder.read(Unknown Source)
at java.io.InputStreamReader.read(Unknown Source)
at java.io.BufferedReader.fill(Unknown Source)
at java.io.BufferedReader.readLine(Unknown Source)
at java.io.BufferedReader.readLine(Unknown Source)
at zad41.ServerThread.run(ServerThread.java)

public void communicate(){
    	System.out.println("Communication starts!");
     
        String fromServer="Receiving data form server";
    	 try {
			while ((fromServer = in.readLine()) != null) {
			     System.out.println("Server: " + fromServer);
			     output.setText(fromServer);
			     if (fromServer.equals("Bye."))
			         break;
			  
			if (action != null) {
			         System.out.println("Client: " + action);


			       
			         
			         
			         if(lastname!=null){
			         	out.println(action+":"+lastname);
			         	out.flush();
			         }
			         
			        
			         
			         if(number_with!=null){
			        	 String info[]=number_with.split(" ");
			         	out.println(action+":"+info[0]+":"+info[1]);
			         	out.flush();
	                   }
			           }
			 }
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    }