How to validate a server in client-server application

I am considering a client server application for a masters project. One of the core requirements for this application would be to ensure that the server could not be replaced. This would be easy to do using public/private keys. The client creates a message and encrypts using servers public key, then sends to the server. The server decrypts, processes, creates response, and encrypts using its private key. This works, however the public and private keys need to be in the source code. It looks like keystores may fix that problem, however the password to the key store would then be required. For this application to be usefull, I need to find a way to embed a password or encryption key in a .classfile in a way that it can not be retrieved by decompiling or parsing for strings. Anyone have ideas on how this could be done, or a different method I could use to guarantee that the response coming from a server process is from my server program and not a fake program?

More detail. The program is a network license server (not web based). We need a simple license server for internal use, so that we can track usage and limit concurrent users for custom software. We also need some security so that people can not take the software home and use it. We have looked at commercial applications, however they are very expensive and we can not justify the cost since this is for internal software. There are 3 main pieces to a license server, the client libraries, the server, and the key generator. For the license server to be usefull, it should be impossible (or very very difficult) for someone to generate their own keys and add them to the license server. It should also be very difficult for them to create a fake license server that will grant licenses to clients without needing keys. If public/private key encryption is used, then the client would need to know the servers public key and their private key. These keys would need to be compiled into the program, stored in a key store, or looked up at run time from some other resource. The server would need to know its private key, and the clients public key. Since this is internal software, we can limit access to the server software, so it would be ok to compile the keys into the code (not ideal but secure enough for out use). However if I use this program as my Masters project, I would need to figure out a better way to secure it. The generic problem is how to give someone two programs that talk to each other, and be able to ensure that they do not fake one of the programs?

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RichTextBox1.ScrollToCaret()
End Sub
Private Sub ButtonClear_Click(sender As Object, e As EventArgs) Handles ButtonClear.Click
RichTextBox1.Clear()
InputTextBox.Clear()
End Sub
End Class
Public Class ConnectionInfo
Private _AppendMethod As Action(Of String)
Public ReadOnly Property AppendMethod As Action(Of String)
Get
Return _AppendMethod
End Get
End Property
Private _Client As TcpClient
Public ReadOnly Property Client As TcpClient
Get
Return _Client
End Get
End Property
Private _Stream As NetworkStream
Public ReadOnly Property Stream As NetworkStream
Get
Return _Stream
End Get
End Property
Private _LastReadLength As Integer
Public ReadOnly Property LastReadLength As Integer
Get
Return _LastReadLength
End Get
End Property
Private _Buffer(63) As Byte
Public Sub New(address As IPAddress, port As Integer, append As Action(Of String))
_AppendMethod = append
_Client = New TcpClient
_Client.Connect(address, port)
_Stream = _Client.GetStream
End Sub
Public Sub AwaitData()
_Stream.BeginRead(_Buffer, 0, _Buffer.Length, AddressOf DoreadData, Me)
End Sub
Public Sub Close()
If _Client IsNot Nothing Then _Client.Close()
_Client = Nothing
_Stream = Nothing
End Sub
Private Sub DoreadData(result As IAsyncResult)
Dim info As ConnectionInfo = CType(result.AsyncState, ConnectionInfo)
Try
If info._Stream IsNot Nothing AndAlso info._Stream.CanRead Then
info._LastReadLength = info._Stream.EndRead(result)
If info._LastReadLength > 0 Then
Dim message As String = System.Text.Encoding.ASCII.GetString(info._Buffer)
info._AppendMethod(message)
End If
info.AwaitData()
End If
Catch ex As Exception
info._LastReadLength = -1
info._AppendMethod(ex.Message)
End Try
End Sub
End Class
//ScreenShot server
http://prntscr[dot]com/5t1ol3
//Screenshot client
http://prntscr[dot]com/5t1odj
source: code[dot]msdn[dot]microsoft[dot]com/windowsdesktop/Simple-Multi-User-TCPIP-43cc3b44

I have a similar chat application. When the user attempts to connect, instead of sending a simple string, the client sends a serialized object(xml string) with all relevant login and session information, this includes the user's IP address. Once the server
receives said information, depending on the type of TCP broadcast (a custom enumerated type) information from one user may be passed to a single user, or distributed to many users.
If it helps, here is the TCPBroadcast object I use. But in order for your server to understand it, you kind of have to build your server and client somewhat around it.
Option Strict On
Option Explicit On
Option Infer Off
Namespace TCPChat
Public Class TCPBroadcast
Public Property Message As String
Public Property BroadCastTime As DateTime
Public Property DestUser As String
Public Property OriginUser As String
Public Property PasswordHash As String
Public Property BroadcastSourceIP As String
Public Property BroadCastType As TCPBroadcastType
Public Property LoginUserName As String
Public Property FailureReason As String
Public Function XmlEncoding() As String
Dim serializer As New Xml.Serialization.XmlSerializer(GetType(TCPBroadcast))
Dim XML As String = String.Empty
Using memStream As New IO.MemoryStream
Using xmlWriter As New Xml.XmlTextWriter(memStream, System.Text.Encoding.UTF8) With _
{.Indentation = 4, .Formatting = System.Xml.Formatting.Indented}
serializer.Serialize(xmlWriter, Me)
End Using
XML = System.Text.Encoding.UTF8.GetString(memStream.ToArray)
End Using
Return XML
End Function
Public Function ToBinary() As Byte()
Return System.Text.Encoding.UTF8.GetBytes(Me.XmlEncoding)
End Function
Public Shared Function FromBinary(binary As Byte()) As DeserializationResult
Dim xml As String = System.Text.Encoding.UTF8.GetString(binary)
Return FromXML(xml)
End Function
Public Shared Function FromXML(xml As String) As DeserializationResult
Dim DeserializationResult As New DeserializationResult
DeserializationResult.Error = False
Try
Dim deserializer As New Xml.Serialization.XmlSerializer(GetType(TCPBroadcast))
Dim buffer As Byte() = System.Text.Encoding.UTF8.GetBytes(xml)
Using memStream As New IO.MemoryStream(buffer)
DeserializationResult.tcpBroadCast = CType(deserializer.Deserialize(memStream), TCPBroadcast)
End Using
Catch ex As Exception
DeserializationResult.Error = True
DeserializationResult.ErrorMessage = ex.ToString
DeserializationResult.AttemptedXML = xml
End Try
Return DeserializationResult
End Function
Public Class DeserializationResult
Public [Error] As Boolean
Public ErrorMessage As String
Public tcpBroadCast As TCPBroadcast
Public AttemptedXML As String
Sub New()
End Sub
End Class
Public Enum TCPBroadcastType
AdministrativeMessage
AuthenticationFailure
AuthenticationSuccess
ChatBroadcast
CredentialsRequest
Credentials
DisconnectedByServer
KeepAlive
PrivateMessage
ServerMessage
SystemMessage
UnableToProcessRequest
End Enum
End Class
End Namespace
“If you want something you've never had, you need to do something you've never done.”
Don't forget to mark
helpful posts and answers
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new article
about it! My Articles
*This post does not reflect the opinion of Microsoft, or its employees.

Distributed system concept, how 2 server link up and serve a client

here are my code...
import java.io.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
public class Server extends JFrame{
     private JTextArea jta=new JTextArea();
     public static void main (String[] args){
          new Server(); //launch server
     public Server(){//construct a server class
     getContentPane().setLayout (new BorderLayout());
     getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);
     setTitle("Server");
     setSize(500,300);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setVisible(true);
     try{
     //create a server socket
          ServerSocket serverSocket=new ServerSocket(8000); //server scoket
          jta.append("Server started" +"........"+'\n');
          //listen for a connection request
          Socket socket=serverSocket.accept(); //connect client
          //create data input and output stream
     DataInputStream inputFromClient=new DataInputStream(socket.getInputStream());//input from client
     DataOutputStream outputToClient=new DataOutputStream(socket.getOutputStream());//output to client
     while(true){ // while true, server wait user input
          jta.append("Server waiting input from client" +"........"+'\n');
          Calendar calendar = Calendar.getInstance();
         int GMT = calendar.get(Calendar.HOUR_OF_DAY); //time
         long totalMilliseconds=System.currentTimeMillis();
         long totalSeconds=totalMilliseconds/1000;
         int currentSecond=(int)(totalSeconds%60); //GMT seconds
          long totalMinutes=totalSeconds/60;
          int currentMinute=(int)(totalMinutes%60);     //GMT minutes
          long totalHours=(totalMinutes/60);
          int currentHour=(int)(totalHours%24);
          int Hour=(currentHour+8)%24; // GMT HOUR
         String c=""; // c for country
          int option = inputFromClient.read();//getinput perform country selection
          if(option==1){
               c="Africa";
          if(option==2){
               c="Australia";
          if(option==3){
               c="Adelaide";
          if(option==4){
               c="Chaina";
          if(option==5){
               c="Korea";
          if(option==6){
               c="Chicago";
          if(option==7){
               c="New York";
          if(option==8){
               c="Caracas";
          if(option==9){
               c="Rio De Janeira";
          if(option==10){
               c="Racife";
          if(option==11){
               c="Azores";
          if(option==12){
               c="London";
          if(option==13){
               c="Paris";
          if(option==14){
               c="Cairo";
          if(option==15){
               c="Moscow";
          if(option==16){
               c="Baku";
          if(option==17){
               c="Karachi";
          if(option==8){
               c="Dhaka";
          if(option==19){
               c="Bangkok";
          if(option==20){
               c="Tokyo";
          jta.append("Client select: " + c +'\n');
switch(option)//read desire destination, and perform calculation, GMT time base on LONDON
         case 1:
         GMT=currentHour+1;
         jta.append("Africa time now is " + GMT+ ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
             case 2:
         GMT=currentHour+8;
         outputToClient.writeInt(GMT);
             jta.append("Australia time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         break;
         case 3:
         GMT=currentHour+9;
         outputToClient.writeInt(GMT);
         jta.append("Adelaide time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         break;
         case 4:
         GMT=currentHour+8;
         outputToClient.writeInt(GMT);
         jta.append("Chaina time now is " + GMT + ":" +currentMinute + ":" + currentSecond +"\n");
         break;
         case 5:
         GMT=currentHour+9;
         outputToClient.writeInt(GMT);
         jta.append("Korea time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 6:
         GMT=currentHour-6;
         outputToClient.writeInt(GMT);
         jta.append("Chicago time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 7:
          GMT=currentHour-5;
         jta.append("New York time now is " + GMT + ":" +currentMinute + ":"+currentSecond +"\n");
         outputToClient.writeInt(GMT);
          break;
         case 8:
         GMT=currentHour-4;
         outputToClient.writeInt(GMT);
         jta.append("Caracas time now is " + GMT + ":"+ currentMinute + ":"+currentSecond +"\n");
            break;
         case 9:
         GMT=currentHour-3;
         outputToClient.writeInt(GMT);
         jta.append("Rio De Janeiro time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 10:
         GMT=currentHour-2;
         outputToClient.writeInt(GMT);
         jta.append("Recife time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 11:
         GMT=currentHour-1;
         outputToClient.writeInt(GMT);
         jta.append("Azores time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
            break;
         case 12:
         GMT=currentHour;
         outputToClient.writeInt(GMT);
             jta.append("London time now is " + GMT + ":"+ currentMinute + ":" + currentSecond +"\n");
          break;
         case 13:
         GMT=currentHour+1;
         outputToClient.writeInt(GMT);
         jta.append("Paris time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 14:
         GMT=currentHour+2;
         outputToClient.writeInt(GMT);
         jta.append("Cairo time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 15:
         GMT=currentHour+3;
         outputToClient.writeInt(GMT);
         jta.append("Moscow time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
             break;
         case 16:
         GMT=currentHour+4;
         jta.append("Baku time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
         case 17:
             GMT=(currentHour+5)%24;
         jta.append("Karachi time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
         case 18:
         GMT=(currentHour+6)%24;
         jta.append("Dhaka time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
          break;
         case 19:
         GMT=(currentHour+8)%24;
         jta.append("Hong Kong time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          outputToClient.writeInt(GMT);
          break;
         case 20:
         GMT=(currentHour+9)%24;
         jta.append("Tokyo time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
         }//end switch
            //export HOUR, minute,second to client side
         outputToClient.writeInt(GMT);
         outputToClient.writeInt(currentMinute);
         outputToClient.writeInt(currentSecond);
          jta.append("Option Found "+ c +'\n');
          catch(IOException ex){
          System.err.println(ex);
}//end constructor
}//end server class
//server 2
import java.io.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
public class Server2 extends JFrame{
     private JTextArea jta=new JTextArea();
     public static void main (String[] args){
          new Server(); //launch server
     public Server2(){//construct a server class
     getContentPane().setLayout (new BorderLayout());
     getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);
     setTitle("Server");
     setSize(500,300);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setVisible(true);
     try{
     //create a server socket
          ServerSocket serverSocket1=new ServerSocket("127.0.0.2",8001); //server scoket
          jta.append("Server2 started" +"........"+'\n');
          //listen for a connection request
          Socket socket=serverSocket1.accept(); //connect client
     //     Socket socket1=serverSocket.accept();
          //create data input and output stream
     DataInputStream inputFromClient=new DataInputStream(socket.getInputStream());//input from client
     DataOutputStream outputToClient=new DataOutputStream(socket.getOutputStream());//output to client
     while(true){ // while true, server wait user input
          jta.append("Server waiting input from client" +"........"+'\n');
          Calendar calendar = Calendar.getInstance();
         int GMT = calendar.get(Calendar.HOUR_OF_DAY); //time
         long totalMilliseconds=System.currentTimeMillis();
         long totalSeconds=totalMilliseconds/1000;
         int currentSecond=(int)(totalSeconds%60); //GMT seconds
          long totalMinutes=totalSeconds/60;
          int currentMinute=(int)(totalMinutes%60);     //GMT minutes
          long totalHours=(totalMinutes/60);
          int currentHour=(int)(totalHours%24);
          int Hour=(currentHour+8)%24; // GMT HOUR
         String c=""; // c for country
          int option = inputFromClient.read();//getinput perform country selection
          if(option==1){
               c="Africa";
          if(option==2){
               c="Australia";
          if(option==3){
               c="Adelaide";
          if(option==4){
               c="Chaina";
          if(option==5){
               c="Korea";
          if(option==6){
               c="Chicago";
          if(option==7){
               c="New York";
          if(option==8){
               c="Caracas";
          if(option==9){
               c="Rio De Janeira";
          if(option==10){
               c="Racife";
          if(option==11){
               c="Azores";
          if(option==12){
               c="London";
          if(option==13){
               c="Paris";
          if(option==14){
               c="Cairo";
          if(option==15){
               c="Moscow";
          if(option==16){
               c="Baku";
          if(option==17){
               c="Karachi";
          if(option==8){
               c="Dhaka";
          if(option==19){
               c="Bangkok";
          if(option==20){
               c="Tokyo";
          jta.append("Client select: " + c +'\n');
switch(option)//read desire destination, and perform calculation, GMT time base on LONDON
         case 1:
         GMT=currentHour+1;
         jta.append("Africa time now is " + GMT+ ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
             case 2:
         GMT=currentHour+8;
         outputToClient.writeInt(GMT);
             jta.append("Australia time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         break;
         case 3:
         GMT=currentHour+9;
         outputToClient.writeInt(GMT);
         jta.append("Adelaide time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         break;
         case 4:
         GMT=currentHour+8;
         outputToClient.writeInt(GMT);
         jta.append("Chaina time now is " + GMT + ":" +currentMinute + ":" + currentSecond +"\n");
         break;
         case 5:
         GMT=currentHour+9;
         outputToClient.writeInt(GMT);
         jta.append("Korea time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 6:
         GMT=currentHour-6;
         outputToClient.writeInt(GMT);
         jta.append("Chicago time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 7:
          GMT=currentHour-5;
         jta.append("New York time now is " + GMT + ":" +currentMinute + ":"+currentSecond +"\n");
         outputToClient.writeInt(GMT);
          break;
         case 8:
         GMT=currentHour-4;
         outputToClient.writeInt(GMT);
         jta.append("Caracas time now is " + GMT + ":"+ currentMinute + ":"+currentSecond +"\n");
            break;
         case 9:
         GMT=currentHour-3;
         outputToClient.writeInt(GMT);
         jta.append("Rio De Janeiro time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 10:
         GMT=currentHour-2;
         outputToClient.writeInt(GMT);
         jta.append("Recife time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 11:
         GMT=currentHour-1;
         outputToClient.writeInt(GMT);
         jta.append("Azores time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
            break;
         case 12:
         GMT=currentHour;
         outputToClient.writeInt(GMT);
             jta.append("London time now is " + GMT + ":"+ currentMinute + ":" + currentSecond +"\n");
          break;
         case 13:
         GMT=currentHour+1;
         outputToClient.writeInt(GMT);
         jta.append("Paris time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 14:
         GMT=currentHour+2;
         outputToClient.writeInt(GMT);
         jta.append("Cairo time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          break;
         case 15:
         GMT=currentHour+3;
         outputToClient.writeInt(GMT);
         jta.append("Moscow time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
             break;
         case 16:
         GMT=currentHour+4;
         jta.append("Baku time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
         case 17:
             GMT=(currentHour+5)%24;
         jta.append("Karachi time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
         case 18:
         GMT=(currentHour+6)%24;
         jta.append("Dhaka time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
          break;
         case 19:
         GMT=(currentHour+8)%24;
         jta.append("Hong Kong time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
          outputToClient.writeInt(GMT);
          break;
         case 20:
         GMT=(currentHour+9)%24;
         jta.append("Tokyo time now is " + GMT + ":" + currentMinute + ":" + currentSecond +"\n");
         outputToClient.writeInt(GMT);
             break;
         }//end switch
            //export HOUR, minute,second to client side
         outputToClient.writeInt(GMT);
         outputToClient.writeInt(currentMinute);
         outputToClient.writeInt(currentSecond);
          jta.append("Option Found "+ c +'\n');
          catch(IOException ex){
          System.err.println(ex);
}//end constructor
}//end server2 class
//client class
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
public class Client extends JFrame implements ActionListener{
     private JTextField jtf =new JTextField();//text feild for receiving option
     private JTextArea jta=new JTextArea();//text area display contents
     private JButton btnDownload=new JButton("Download");
     //IO stream
     private DataOutputStream toServer;
     private DataInputStream fromServer;
     public static void main(String [] args){
          new Client();        //launch client
     public Client(){//construct a client class
         //display layout
          JPanel p=new JPanel();
          p.setLayout(new GridLayout(1,3));
         p.add(new JLabel("Select file name:"));
         p.add(jtf, BorderLayout.NORTH);
         p.add (btnDownload);
          p.add (new JButton("RESUME"));
          p.add(new JButton("STOP"));
         jtf.setHorizontalAlignment(JTextField.LEFT);
         getContentPane().setLayout(new BorderLayout()); //set borderlayout
        getContentPane().add(p, BorderLayout.NORTH);
         getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);
         //     btnDownload.addActionListener(this);
         jtf.addActionListener(this); //perform action
         setTitle("Client"); //interface title
         setSize(600,300); //interface size
         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         setVisible(true);
         try{
          //create a client socket
          Socket socket=new Socket("localhost",8000);
    //      Socket socket1=new Socket("127.0.0.2",8001);
          jta.append("Client started.....\n" +"your locale time is " + new Date()+ '\n');
          fromServer=new DataInputStream(socket.getInputStream()); //initialize get from server
          toServer=new DataOutputStream(socket.getOutputStream()); //initialize to server
          catch(IOException ex){ //error if server timeout
               jta.append(ex.toString()+'\n');
     public void actionPerformed(ActionEvent e){ //action perform when user hit enter
          String actionCommand=e.getActionCommand();
          if(e.getSource() instanceof JTextField){
               try{
                    int option=Integer.parseInt(jtf.getText().trim());//convert text to integer
                    String c=""; //c for country list
                    toServer.write(option);//write selection and sent to server
                    toServer.flush(); //server refresh
                    int inputFromServer = fromServer.readInt();//initilize read data from server, integer format
          //if ...selection to determine the country user desire
          if(option==1){
               c="Africa";
          if(option==2){
               c="Australia";
          if(option==3){
               c="Adelaide";
          if(option==4){
               c="Chaina";
          if(option==5){
               c="Korea";
          if(option==6){
               c="Chicago";
          if(option==7){
               c="New York";
          if(option==8){
               c="Caracas";
          if(option==9){
               c="Rio De Janeira";
          if(option==10){
               c="Racife";
          if(option==11){
               c="Azores";
          if(option==12){
               c="London";
          if(option==13){
               c="Paris";
          if(option==14){
               c="Cairo";
          if(option==15){
               c="Moscow";
          if(option==16){
               c="Baku";
          if(option==17){
               c="Karachi";
          if(option==8){
               c="Dhaka";
          if(option==19){
               c="Bangkok";
          if(option==20){
               c="Tokyo";
          jta.append("Selected: "+ c +'\n');
                    int GMT = fromServer.readInt();     //hour import from server
                  int currentMinute = fromServer.readInt();//minute import from server
                    int currentSecond = fromServer.readInt();// second from server
                    //print full time format in JtextArea
                    jta.append("Time is >>"+GMT+ ":" +currentMinute+ ":" +currentSecond+'\n');
               catch (IOException ex){
                    System.err.println(ex);
          }// end if ..true
     }// end actiond
}//end client class

here i attach my similar code again, which can compile..
problem is, how to let this server to communicate with each other, if i duplicate my server code. Which mean 2 server.
import java.io.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
public class Server extends JFrame{
     private JTextArea jta=new JTextArea();
     public static void main (String[] args){
          new Server(); //launch server
     public Server()
     {//construct a server class
     getContentPane().setLayout (new BorderLayout());
     getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);
     setTitle("Server");
     setSize(500,300);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setVisible(true);
     try{
     //create a server socket
          ServerSocket serverSocket=new ServerSocket(8000); //server scoket
          jta.append("Server started" +"........"+'\n');
          //listen for a connection request
          Socket socket=serverSocket.accept(); //connect client
     DataInputStream inputFromClient=new DataInputStream(socket.getInputStream());//input from client
     DataOutputStream outputToClient=new DataOutputStream(socket.getOutputStream());//output to client
     while(true){ // while true, server wait user input
          jta.append("Server waiting input from client" +"........"+'\n');
                     jta.append("Option Found "+ '\n');
          catch(IOException ex){
          System.err.println(ex);
}

How can i check the office web app server(wac client) is calling custom WOPI host?

I am getting an error when I testing my wopi host(which is the same as
example) with Office Web app server "Sorry, there was a problem and we can't open this document. If this happens again, try opening the document in Microsoft Word."
1-how can find the log files of this error?
2-how can i check the office web app server(wac client) is calling my WOPI host?
I am not sure about cumunication between owa to wopi host. I actually dont know how to implement checkfile and getfile functions to wopi host for waiting for call back from owa client.
Note:I am sure that office web app server is configured true. Because i test it with sharepoint 2013 and editing and viewing is working well.

Hi,
According to your post, my understanding is that
CheckFileInfo is how the WOPI application gets information about the file and the permissions a user has on the file. It should have a URL that looks like this:
HTTP://server/<...>/wopi*/files/<id>?access_token=<token>
While CheckFileInfo provides information about a file, GetFile returns the file itself. It should have a URL that looks like this:
HTTP://server/<...>/wopi*/files/<id>/contents?access_token=<token>
There is a great article for your reference.
http://blogs.msdn.com/b/officedevdocs/archive/2013/03/20/introducing-wopi.aspx
You can also refer to the following article which is about building an Office Web Apps(OWA) WOPI Host.
http://blogs.msdn.com/b/scicoria/archive/2013/07/22/building-an-office-web-apps-owa-wopi-host.aspx
Thanks & Regards,
Jason
Jason Guo
TechNet Community Support

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