LBR iiwa TCP/IP communication issue

Giuseppe Cappellacci · March 18, 2019 at 5:29 PM

Hi everyone,

I am working with KUKA LBR iiwa by using SunRise Workbench and I need to connect the robot with another device using a TCP/IP protocol. I am writing a TCP/IP server and a TCP/IP client using java sockets. Actually, when I use the robot as the server, I am able to establish a connection using my laptop as client. But when I try the opposite task (robot-client and laptop-server), it says "Connection timed out: connect".

Is there anyone who can give me any advise?

Thanks in advance,

Here is the client code:

public class LBR_Client {
private PrintStream out = null;
private BufferedReader in = null;
@Override
public void initialize() {
Socket socket = null;
try {
socket = new Socket("172.31.1.14", 30001);

in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintStream(new BufferedOutputStream(socket.getOutputStream()), true);
out.println("client message");

System.out.print("server message: " + in);

out.close();
in.close();
socket.close();

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

@Override
public void run() {
}
}

And here's the server code:

public class MyServer {
public static void main(String args[]) throws IOException{
Socket client;
BufferedReader in = null;
PrintStream out = null;
try {
ServerSocket server = new ServerSocket(30001);
client = server.accept();
server.close();
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out = new PrintStream(new BufferedOutputStream(client.getOutputStream()), true);
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));

String userInput;
userInput = stdIn.readLine();
out.println(userInput);

System.out.print("Client message: " + in);

stdIn.close();
out.close();
in.close();

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

DrG · March 25, 2019 at 5:54 PM

Hi Giuseppe Capellacci,

Quote

I am writing a TCP/IP server and a TCP/IP client using java sockets. Actually, when I use the robot as the server, I am able to establish a connection using my laptop as client. But when I try the opposite task (robot-client and laptop-server), it says "Connection timed out: connect".

Hm.. the communication should be "symmetric" feasible.

I would check the Network/Firewall Settings on the Laptop, since a lot of those Firewall-Systems distinguish between outbound and inbound traffic - aka: who is the Server and who is the client.
Therefore, as you open the socket ports in your Firewall, you can configure for "incoming" or "outgoing" in separate views.

For an simple test: Deactivate the Firewall of the Laptop for the Duration of your test, and rerun the Client/Server Programs.

A quick glance on your code: It seems ok, unless:
I personally would not immediately close (server.close()) the Server socket directly after first Connection of the Client ("Server.accept()"), but keep the Server running in an endless Loop reentering "accept()" as soon as the Client finishes - this saves a lot of Manual "restart" work.

Therefore: In your program, the Server MUST be started before the clienat - and each time a Client connects...
... you could reduce this pain..

Hope that helps,
DrG

matteopantano · April 16, 2019 at 6:29 PM

I have the same issue. Did you solve?

kiiwa · April 16, 2019 at 7:11 PM

You're closing the server socket, too early, before even reading from the input stream. And you're printing the object BufferedReader in, instead of reading from the stream. google some simple TCP server/client examples and build on them.

Code

System.out.print("server message: " + in);

kiiwa · April 16, 2019 at 7:22 PM

Here's a simple example that works.

Client on Robot:

Java

package apps; 
 import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket; 
import javax.inject.Inject; 
import com.kuka.roboticsAPI.applicationModel.RoboticsAPIApplication; 
import com.kuka.roboticsAPI.controllerModel.Controller;


public class LBR_Client extends RoboticsAPIApplication {
	@Inject
	private Controller contoller;  
	Socket clientSocket = null;


	@Override
	public void initialize() { 
		contoller = (Controller) getContext().getControllers().toArray()[0]; 
	}


	@Override
	public void run() 
	{
		try {       
			String sentence;
			String modifiedSentence;
			BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
			clientSocket = new Socket("172.31.1.135", 30000);
			DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
			BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
			sentence = "tcp message";
			outToServer.writeBytes(sentence + '\n');
			modifiedSentence = inFromServer.readLine();
			System.out.println("FROM SERVER: " + modifiedSentence);
			clientSocket.close(); 
		} catch (IOException e) {  
			e.printStackTrace();            
		}  
	}  
	// To liberate the port 
	@Override
	public void dispose()
	{
		try { 
			clientSocket.close();  
			System.out.println("Socket closed"); 
		}catch (Exception e)
		{ e.printStackTrace(); } 
		super.dispose(); 
	} 


}

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Server on PC:

Java

package tcp;


import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.*;


class MyServer {
 public static void main(String argv[]) throws Exception {
  String clientSentence;
  String capitalizedSentence;
  ServerSocket welcomeSocket = new ServerSocket(30000);


  while (true) {
   Socket connectionSocket = welcomeSocket.accept();
   BufferedReader inFromClient =  new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
   DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
   clientSentence = inFromClient.readLine();
   System.out.println("Received: " + clientSentence);
   capitalizedSentence = clientSentence.toUpperCase() + '\n';
   outToClient.writeBytes(capitalizedSentence);
  }
 }
}

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matteopantano · April 17, 2019 at 8:45 AM

Thanks kiiwa. However, the problem is still not solved.

My code is the following:

Code

public void socketConnection()  // Connecting to server at 172.31.1.50 Port:30001
	{
		System.out.println("Connecting to server at 172.31.1.50 Port:30001");

		while (true){
			try{
			    skt = new Socket("172.31.1.50", 30001); 

			    BufferedReader inFromServer = new BufferedReader(new InputStreamReader(skt.getInputStream()));
			    System.out.println("FROM SERVER: " + inFromServer.readLine());

			    System.out.println("KUKA iiwa is connected to the server.");
		    	    break;
			}
			catch(IOException e){
		            System.out.println("ERROR connecting to the server!");
		            e.printStackTrace();
			}
		}


	    try{
	    	outputStream = new PrintWriter(skt.getOutputStream(), true);
	    	inputStream = new BufferedReader(new InputStreamReader(skt.getInputStream()));
	    	RUN = true;
	    }
	    catch(IOException e)
	    {
	    	System.out.println("Error creating inPort and outPort");
	    	e.printStackTrace();
	    }
	}

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The code then throws the first exception.

In attachment a Wireshark capture of the network.

KUKA IP: 172.31.1.147
PC IP: 172.31.1.50

BR,

Matteo

matteopantano · April 17, 2019 at 10:30 AM

Solved, it was a problem with firewall rules.

For the sake of clarity someone should or disable firewall or create an inbound policy that allows communication from iiwa port to the port of the laptop.

kiiwa · April 17, 2019 at 11:36 AM

Good!
Yes, the firewall is a pain in the neck sometimes.

rreype314 · August 6, 2019 at 2:06 AM

As a note on the same topic: port numbers are also a source of problems, you can only use port numbers between 30,000-30,010

JM212 · December 4, 2020 at 8:25 PM

Quote from kiiwa

Here's a simple example that works.

Client on Robot:

Java

package apps; 
 import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket; 
import javax.inject.Inject; 
import com.kuka.roboticsAPI.applicationModel.RoboticsAPIApplication; 
import com.kuka.roboticsAPI.controllerModel.Controller;


public class LBR_Client extends RoboticsAPIApplication {
	@Inject
	private Controller contoller;  
	Socket clientSocket = null;


	@Override
	public void initialize() { 
		contoller = (Controller) getContext().getControllers().toArray()[0]; 
	}


	@Override
	public void run() 
	{
		try {       
			String sentence;
			String modifiedSentence;
			BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
			clientSocket = new Socket("172.31.1.135", 30000);
			DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
			BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
			sentence = "tcp message";
			outToServer.writeBytes(sentence + '\n');
			modifiedSentence = inFromServer.readLine();
			System.out.println("FROM SERVER: " + modifiedSentence);
			clientSocket.close(); 
		} catch (IOException e) {  
			e.printStackTrace();            
		}  
	}  
	// To liberate the port 
	@Override
	public void dispose()
	{
		try { 
			clientSocket.close();  
			System.out.println("Socket closed"); 
		}catch (Exception e)
		{ e.printStackTrace(); } 
		super.dispose(); 
	} 


}

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Server on PC:

Java

package tcp;


import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.*;


class MyServer {
 public static void main(String argv[]) throws Exception {
  String clientSentence;
  String capitalizedSentence;
  ServerSocket welcomeSocket = new ServerSocket(30000);


  while (true) {
   Socket connectionSocket = welcomeSocket.accept();
   BufferedReader inFromClient =  new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
   DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
   clientSentence = inFromClient.readLine();
   System.out.println("Received: " + clientSentence);
   capitalizedSentence = clientSentence.toUpperCase() + '\n';
   outToClient.writeBytes(capitalizedSentence);
  }
 }
}

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Is it a safe assumption that the Client and server are interchangable on pc and robot?

Seulki · December 8, 2020 at 8:44 AM

Quote from JM212

Is it a safe assumption that the Client and server are interchangable on pc and robot?

Yes, as long as you use right ports.

LBR iiwa TCP/IP communication issue

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