Question

I’ve been trying to get a basic socket connection working between my server and phone. The following code works on the Android emulator perfectly, but when I try it on my phone, it fails and I have no idea why. I’ve tried most suggestions I could find on SO and Google and none of them work.

My server code is just some basic Ruby:
require ‘socket’

server = TCPServer.new 2000

puts 'Server started!'
loop do
Thread.start(server.accept) do |client|
puts "Received client"

client.write "Connection established."

    while text = client.gets
        puts text
        client.puts text # Just echo the result back...
    end

    client.close
  end
end

And my client code is as follows:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

    try{
        Socket s = new Socket("***", 2000);

        BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));

        PrintWriter out = new PrintWriter(s.getOutputStream());

        out.println("test\r\n"); 
        out.flush();
        out.close();            


    }catch(Exception e){

    }

}

The code returns the expected response on the emulator:

Server started!
Received client
test

But when I run it on my phone, it only returns:

Server started!
Received client

Clearly it is establishing the connection. I have some more in-depth code that I wrote, that also writes back to the server, and again, the emulator writes & receives, but my phone does neither, after a while, my phone reports: “Connection closed by peer.”

Any ideas would be great!

Edit: it seems to work on my friend’s phone… so now I’m even more stumped… I’m using a Sony Xperia

Answer 1

Turns out there is a problem with port 2000 on the carrier MTN. Using another port solved my problem.