I've been using a simple eclipse plugin to create visual state machines, called statecharts, that also uses Java code to work. My overall goal is to make two state machines communicate with each other through sockets and exchange data and make transitions based on that, such as a client-server communication.
In the beginning I was using simple synchronous client-server code, but apparently using a synchronous approach can not help; the correct way is to continuously poll data from a queue. I'm now trying to use Java NIO which seems promising, but unfortunately had no success in the first attempt. It seems like there is a busy loop somewhere that doesn't allow the received value to trigger the change.
The code is pretty simple: I first try to connect to server (it works), send a data (it works), and try to read from input buffer every cycle as a way to receive data as you can see in the picture. The logic so far makes sense. I set the received data to a variable which also is located in a transition expression. So basically whenever it is set true, I should transit to next state. But it doesn't work.
Can someone help me solve this problem? I've seen there are async APIs like Netty and Naga that might make things easier if that is a remedy.
Here is a visual scheme of a state machine:
Here is the code for client:
package test;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class EchoClient2 {
String serverHostname = new String("127.0.0.1");
BufferedReader stdIn;
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
public void open(){
System.out.println("Attemping to connect to host " + serverHostname
+ " on port 5555.");
try {
echoSocket = new Socket(serverHostname, 5555);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(
echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: " + serverHostname);
} catch (IOException e) {
System.err.println("Couldn't get I/O for " + "the connection to: "
+ serverHostname);
}
}
public void send(){
String userInput = "1";
out.println(userInput);
}
public String receive(){
String result = "";
try {
result = in.readLine();
if(result==null)
return "0";
} catch (IOException e) {
}
return result;
}
}
and here is the code for server:
package test;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class EchoServer extends Thread {
protected Socket clientSocket;
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(5555);
System.out.println("Connection Socket Created");
try {
while (true) {
System.out.println("Waiting for Connection");
new EchoServer(serverSocket.accept());
}
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
} catch (IOException e) {
System.err.println("Could not listen on port: 5555.");
System.exit(1);
} finally {
try {
serverSocket.close();
} catch (IOException e) {
System.err.println("Could not close port: 5555.");
System.exit(1);
}
}
}
private EchoServer(Socket clientSoc) {
clientSocket = clientSoc;
start();
}
public void run() {
System.out.println("New Communication Thread Started");
try {
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(),
true);
BufferedReader in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
System.out.println("Server: " + inputLine);
out.println(inputLine);
if (inputLine.equals("Bye."))
break;
}
out.close();
in.close();
clientSocket.close();
} catch (IOException e) {
System.err.println("Problem with Communication Server");
System.exit(1);
}
}
}
And here is the Eclipse project folder that you can simply import if that might be easier.
