But when I used TCPMon to listen two way TCP communication by configuring the listen port and the target port, I observed there is no simultaneous reading and writing for the two paths (from source to target and target to source).
Therefore a simple custom TCPMon is written to facilitate simultaneous read and write. Here is the approach I followed.
To listen from a port we can create a new Socket connection, configure the port and accept data. Here I have taken the listening port as 2389.
public static void main(String[] args) throws Exception {
ServerSocket srcSocket = new ServerSocket(2389);
while (true) {
new Thread(new TCPServer(srcSocket.accept())).start();
}
}
It requires what is the target port that data should be sent to. Here the target port is 3456.
Socket targetSock = new Socket("localhost", 3456);
Then we can have input stream and the output stream from both socket connections.
srcIn = srcSocket.getInputStream(); srcOut = srcSocket.getOutputStream(); targetIn = targetSock.getInputStream(); targetOut = targetSock.getOutputStream();
Then we should pipe data from the input stream to output stream to have no data loss during communication.
private class Pipe extends Thread {
private InputStream in;
private OutputStream out;
public Pipe(InputStream in, OutputStream out) {
this.in = in;
this.out = out;
}
public void run() {
try {
byte[] buff = new byte[512];
int i;
while (true) {
i = in.read(buff);
if (i > 0) {
out.write(buff, 0, i);
System.out.print(".");
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
In order to have simultaneous data writing and reading operations two threads should be started.new Pipe(srcIn, targetOut).start(); new Pipe(targetIn, srcOut).start();
Now our TCPMon works fine with simultaneous data passing.
The full code is shown below.
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class TCPServer implements Runnable {
private InputStream srcIn, targetIn;
private OutputStream srcOut, targetOut;
public TCPServer(Socket srcSocket) throws Exception {
Socket targetSock = new Socket("localhost", 3456);
srcIn = srcSocket.getInputStream();
srcOut = srcSocket.getOutputStream();
targetIn = targetSock.getInputStream();
targetOut = targetSock.getOutputStream();
}
public void run() {
new Pipe(srcIn, targetOut).start();
new Pipe(targetIn, srcOut).start();
}
private class Pipe extends Thread {
private InputStream in;
private OutputStream out;
public Pipe(InputStream in, OutputStream out) {
this.in = in;
this.out = out;
}
public void run() {
try {
byte[] buff = new byte[512];
int i;
while (true) {
i = in.read(buff);
if (i > 0) {
out.write(buff, 0, i);
System.out.print(".");
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) throws Exception {
ServerSocket srcSocket = new ServerSocket(2389);
while (true) {
new Thread(new TCPServer(srcSocket.accept())).start();
}
}
}
