Android Emulator as server in Socket communication

[Asif Kadiwala]

Hi Mark,

In the Socket communication , android emulator as socket client working fine.

But if I configure emulator as Android server and desktop as socket client, then first requirement is to assign an IP address to this emulator instance,

for that I had tried to follow follwing steps to achieve n/w redir but could not succeed.

1). telnet localhost 5554 : works fine and emulator console opened
2). redir add tcp:4444:4444 - it fails to execute then I tried
3).redir tcp:4444:4444 but again the same problem.

So can you please tell me how to achieve IP of the emulator and redirect the ports?? Should I configure default IP 10.0.2.15 to emulator or it takes automatically?? If I have to configure then how??

Please help

[Mark L. Murphy]

Sorry, but I have not experimented with socket/port redirection, so I do not have any advice.

[Fred Grott]

question, did you do a port scan to make sure those ports were open before the redirection?

At them moment that is the only thing I can think of why your command did not work..

[Asif Kadiwala]

Hello,

Can you please tell me how to do port scan before network redirection???

I have not done port redirection , but I had used the same ports for socket communication between Android as client and Desktop as server.It works fine for me. I had released the ports after that.

[Jason Gosling]

I can do Socket Programming on Android with UDP like this

//Class: UDPConnection
package org.anddev.android.udpconnection;

import android.app.Activity;
import android.os.Bundle;

public class UDPConnection extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        new Thread(new Server()).start();
        /* GIve the Server some time for startup */
        try {
               Thread.sleep(500);
          } catch (InterruptedException e) { }
          
        // Kickoff the Client
        new Thread(new Client()).start(); 
    }
}    

  //Class: Client
package org.anddev.android.udpconnection;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import android.util.Log;

public class Client implements Runnable {

	@Override
	public void run() {
		// TODO Auto-generated method stub
		try {
            // Retrieve the ServerName
            InetAddress serverAddr = InetAddress.getByName(Server.SERVERIP);
            
            Log.d("UDP", "C: Connecting...");
            /* Create new UDP-Socket */
            DatagramSocket socket = new DatagramSocket();
            
            /* Prepare some data to be sent. */
            byte[] buf = ("Hello from Client").getBytes();
            
            /* Create UDP-packet with
             * data & destination(url+port) */
            DatagramPacket packet = new DatagramPacket(buf, buf.length, serverAddr, Server.SERVERPORT);
            Log.d("UDP", "C: Sending: '" + new String(buf) + "'");
            
            /* Send out the packet */
            socket.send(packet);
            Log.d("UDP", "C: Sent.");
            Log.d("UDP", "C: Done.");
            
            socket.receive(packet);
            Log.d("UDP", "C: Received: '" + new String(packet.getData()) + "'");

       } catch (Exception e) {
            Log.e("UDP", "C: Error", e);
       } 
	}

}
  

  //Class: Server
package org.anddev.android.udpconnection;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import android.util.Log;

public class Server implements Runnable {
	
	public static final String SERVERIP = "127.0.0.1"; // 'Within' the emulator!
    public static final int SERVERPORT = 4444; 
    
	@Override
	public void run() {
		// TODO Auto-generated method stub
		try {
            /* Retrieve the ServerName */
            InetAddress serverAddr = InetAddress.getByName(SERVERIP);

            Log.d("UDP", "S: Connecting...");
            /* Create new UDP-Socket */
            DatagramSocket socket = new DatagramSocket(SERVERPORT, serverAddr);

            /* By magic we know, how much data will be waiting for us */
            byte[] buf = new byte[17];
            /* Prepare a UDP-Packet that can
             * contain the data we want to receive */
            DatagramPacket packet = new DatagramPacket(buf, buf.length);
            Log.d("UDP", "S: Receiving...");

            /* Receive the UDP-Packet */
            socket.receive(packet);
            
            Log.d("UDP", "S: Received: '" + new String(packet.getData()) + "'");
            Log.d("UDP", "S: Done.");
            
            InetAddress clientAddr = packet.getAddress();
            int clientPort = packet.getPort();
            String s = "Thanks";
            buf = s.getBytes();
            packet = new DatagramPacket(buf, buf.length, clientAddr, clientPort);
            
            Log.d("UDP", "S: Sending: '" + new String(buf) + "'");
            socket.send(packet);

       } catch (Exception e) {
            Log.e("UDP", "S: Error", e);
       } 
	}

}
  

But it can just run onto 1 emulator. I really want to run onto 2 emulators

On the other hand, with Socket Programming, I can not do with TCP

[Anthony Wang]

When I tried to run this progarm I got exception error in creating sockets (both server and client): (in Windows XP professional)
11-21 14:31:45.773: DEBUG/UDP(217): S: Connecting...
11-21 14:31:46.613: DEBUG/UDP(217): C: Connecting...
11-21 14:31:47.323: ERROR/UDP(217): S: Error
11-21 14:31:47.323: ERROR/UDP(217): java.net.SocketException: Permission denied (maybe missing INTERNET permission)
11-21 14:31:47.323: ERROR/UDP(217): at org.apache.harmony.luni.platform.OSNetworkSystem.createDatagramSocketImpl(Native Method)
11-21 14:31:47.323: ERROR/UDP(217): at org.apache.harmony.luni.platform.OSNetworkSystem.createDatagramSocket(OSNetworkSystem.java:90)
11-21 14:31:47.323: ERROR/UDP(217): at org.apache.harmony.luni.net.PlainDatagramSocketImpl.create(PlainDatagramSocketImpl.java:148)
11-21 14:31:47.323: ERROR/UDP(217): at java.net.DatagramSocket.createSocket(DatagramSocket.java:209)
11-21 14:31:47.323: ERROR/UDP(217): at java.net.DatagramSocket.<init>(DatagramSocket.java:107)
11-21 14:31:47.323: ERROR/UDP(217): at com.net.udpconnection.Server.run(Server.java:24)
11-21 14:31:47.323: ERROR/UDP(217): at java.lang.Thread.run(Thread.java:1060)
11-21 14:31:47.563: ERROR/UDP(217): C: Error
11-21 14:31:47.563: ERROR/UDP(217): java.net.SocketException: Permission denied (maybe missing INTERNET permission)
11-21 14:31:47.563: ERROR/UDP(217): at org.apache.harmony.luni.platform.OSNetworkSystem.createDatagramSocketImpl(Native Method)
11-21 14:31:47.563: ERROR/UDP(217): at org.apache.harmony.luni.platform.OSNetworkSystem.createDatagramSocket(OSNetworkSystem.java:90)
11-21 14:31:47.563: ERROR/UDP(217): at org.apache.harmony.luni.net.PlainDatagramSocketImpl.create(PlainDatagramSocketImpl.java:148)
11-21 14:31:47.563: ERROR/UDP(217): at java.net.DatagramSocket.createSocket(DatagramSocket.java:209)
11-21 14:31:47.563: ERROR/UDP(217): at java.net.DatagramSocket.<init>(DatagramSocket.java:88)
11-21 14:31:47.563: ERROR/UDP(217): at java.net.DatagramSocket.<init>(DatagramSocket.java:71)
11-21 14:31:47.563: ERROR/UDP(217): at com.net.udpconnection.Client.run(Client.java:21)
11-21 14:31:47.563: ERROR/UDP(217): at java.lang.Thread.run(Thread.java:1060)

How to correct it?

[DaLi Zhang]

11-21 14:31:47.323: ERROR/UDP(217): java.net.SocketException: Permission denied (maybe missing INTERNET permission)

It seems like you have not add the permission onto your application. try to do this way
In your manifest.xml file, add this sentence
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
you can find other examples from android SDK doc

By the way, the DatagramSocket CAN be created when you are using '127.0.0.1' in emulator, but if you change it to your host machine's IP address, it still report
errors. I have not figure out the reason yet. Hope some other people can help.

Best,
Echo

[Anthony Wang]

Setting up Redirections through the Emulator Console

Each emulator instance provides a control console the you can connect to, to issue commands that are specific to that instance. You can use the redir console command to set up redirections as needed for an emulator instance.

First, determine the console port number for the target emulator instance. For example, the console port number for the first emulator instance launched is 5554. Next, connect to the console of the target emulator instance, specifying its console port number, as follows:

telnet localhost 5554

Once connected, use the redir command to work with redirections. To add a redirection, use:.

redir add <protocol>:<host-port>:<guest-port>

where <protocol> is either tcp or udp, and <host-port> and <guest-port> sets the mapping between your own machine and the emulated system, respectively.

For example, the following command sets up a redirection that will handle all incoming TCP connections to your host (development) machine on 127.0.0.1:5000 and will pass them through to the emulated system's 10.0.2.15:6000.:

redir add tcp:5000:6000

Or UDP
redir add udp:5000:6000

To delete a redirection, you can use the redir del command. To list all redirections for a specific instance, you can use redir list. For more information about these and other console commands, see Using the Emulator Console.

Note that port numbers are restricted by your local environment. this typically means that you cannot use host port numbers under 1024 without special administrator privileges. Also, you won't be able to set up a redirection for a host port that is already in use by another process on your machine. In that case, redir generates an error message to that effect.

[DaLi Zhang]

Hi Anthony,

I used to try the port redirection. The same way as you have written. But I still can not get any incoming message. There will be an error when the system try to do this:

DatagramSocket socket = new DatagramSocket(SERVERPORT, serverAddr);

it only works when the serverAddr is '127.0.0.1'.

If you have successfully set up the connection, can you show me some part of your code?? Thanks a lot.

Best,
Echo

[Anthony Wang]

I use 10.0.2.15.
It works.