Java socket connection problems -

i'm trying learn network programming java , having trouble getting simple chat program connect between server , host. here i'm experiencing:

when try connect client program server i'm getting null pointer exception , won't connect.

while debugging found line

 connection.equals(server.accept()); 

in waitforcommuinication() method in server class not executed.

this occurs when line

client = new socket(inetaddress.getbyname(chatserver), 50499); 

is executed in method connecttoserver() in client class.

i running code using localhost ip add

server class:

public class server extends jframe {  private jtextfield enterfield; private jtextarea displayarea; private objectoutputstream output; private objectinputstream input; private serversocket server; private socket connection; private int counter = 1;  public server() {     super ("server");     enterfield = new jtextfield();     enterfield.seteditable(true);     enterfield.addactionlistener(new actionlistener() {          @override         public void actionperformed(actionevent event) {             senddata(event.getactioncommand());             enterfield.settext("");          }     });      add(enterfield, borderlayout.north);     displayarea = new jtextarea();     add (new jscrollpane(displayarea));      setsize(300,150);     setvisible(true); }    public void runserver() {     try {         server = new serversocket(50499, 100);         //displaymessage("\n listening on port: " + server.getlocalport() + "\n");          while (true) {             try {                 waitforcommunication();                 getstreams();                 processconnection();             } catch (eofexception eofexception) {                 displaymessage("\n server terminated connection ");             } {                 closeconnection();                 ++counter;             }         }     } catch (ioexception ioexception) {         ioexception.printstacktrace();     } }  private void closeconnection() {     displaymessage("\nterminating connection\n");     settextfieldeditable(false);     try {         output.close();         input.close();         connection.close();     } catch (ioexception ioexception) {         ioexception.printstacktrace();     }  }  private void displaymessage(final string string) {     swingutilities.invokelater(new runnable(){          @override         public void run() {             displayarea.append(string);         }      });  }  private void processconnection() throws ioexception {     string message = "connection sucessful";     senddata(message);      settextfieldeditable(true);      {         try {             message = (string) input.readobject();             displaymessage("\n" + message);         } catch (classnotfoundexception classnotfoundexception) {             displaymessage("\nnunknown object type recieved");         }     } while (!message.equals("client>>> terminate")); }  private void settextfieldeditable(final boolean editable) {     swingutilities.invokelater(new runnable(){          @override         public void run() {             enterfield.seteditable(editable);          }      });  }  private void getstreams() throws ioexception {     output = new objectoutputstream(connection.getoutputstream());     output.flush();      input = new objectinputstream(connection.getinputstream());      displaymessage("\ngot i/o stream \n");  }  private void waitforcommunication() throws ioexception {     displaymessage("waiting cennection \n");     connection.equals(server.accept());     displaymessage("connection" + counter + " received from: "             + connection.getinetaddress().gethostname()); }  private void senddata(string message) {     try {         output.writeobject("server>>> " + message);         output.flush();         displaymessage("\nserver>>> " + message);     } catch (ioexception ioexception){         displayarea.append("\nerror writing object");     } } } 

client class:

public class client extends jframe {  private jtextfield enterfield; private jtextarea displayarea; private objectoutputstream output; private objectinputstream input; private string message = ""; private string chatserver;  private socket client;   public client(string host){     super ("host");      chatserver = host;      enterfield = new jtextfield();     enterfield.seteditable(false);     enterfield.addactionlistener(new actionlistener(){          @override         public void actionperformed(actionevent event) {             senddata(event.getactioncommand());             enterfield.settext("");         }      });      add(enterfield, borderlayout.north);      displayarea = new jtextarea();     add(new jscrollpane(displayarea));      setsize(300,150);     setvisible(true); }  public void runclient(){     try{         connecttoserver();         getstreams();         processconnection();     } catch (eofexception eofexception){         displaymessage("\nclient terminated connection");     } catch (ioexception ioexception){         ioexception.printstacktrace();     } {         closeconnection();     } }  private void closeconnection() {     displaymessage("\nclosing connection");      settextfieldeditable(false);      try{         output.close();         input.close();         client.close();     } catch (ioexception ioexception){         ioexception.printstacktrace();     }  }  private void displaymessage(final string messagetodisplay) {     swingutilities.invokelater( new runnable() {          @override         public void run() {             displayarea.append(messagetodisplay);          }      });  }  private void processconnection() throws ioexception {     settextfieldeditable(true);      {         try{             message = (string) input.readobject();         } catch (classnotfoundexception classnotfoundexception){             displaymessage("\nunknown object type recieved");         }     } while (!message.equals("server>>> terminate")); }  private void settextfieldeditable(final boolean b) {     swingutilities.invokelater(new runnable(){          @override         public void run() {             enterfield.seteditable(b);          }     });  }  private void getstreams() throws ioexception {      output = new objectoutputstream(client.getoutputstream());      output.flush();       input = new objectinputstream(client.getinputstream());       displaymessage("\ngot i/o streams!\n"); }  private void connecttoserver() throws ioexception {     displaymessage("attempting connection\n");      client = new socket(inetaddress.getbyname(chatserver), 50499);      displaymessage("connected to: " + client.getinetaddress().gethostname()); }  protected void senddata(string actioncommand) {     try{         output.writeobject("client>>> " + actioncommand);         output.flush();         displaymessage("\nclient>>> " + actioncommand);     } catch (ioexception ioexception){         displayarea.append("\nerror sending message");     }  }  } 

in server class, waitforcommunication method have npe couse of connection null. connection.equals(server.accept());

i'm sure need connection = server.accept();