How to make sockets work in xamarin? - sockets

Question

In the Answer to this question Here:Server Client Application with .NET and Xamarin
the person who answered said: "On Xamarin.Android you can use all of the regular .Net socket classes"
I tried using the code in example of the Microsoft documentation and i had no errors but application just is just displaying like that on the phone:
If I delete the socket code it would display the page normally.My code behind:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using System.Net;
using System.Net.Sockets;
namespace App14
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Page2 : ContentPage
{
public static string data = null;
public static void StartListening()
{
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// Dns.GetHostName returns the name of the
// host running the application.
IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(ipAddress.AddressFamily,
SocketType.Stream, ProtocolType.Tcp);
try
{
listener.Bind(localEndPoint);
listener.Listen(10);
// Start listening for connections.
while (true)
{
var label = new Label() { Text = "searching for a connection" };
// Program is suspended while waiting for an incoming connection.
Socket handler = listener.Accept();
label.Text = "Found a Connection";
data = null;
// An incoming connection needs to be processed.
while (true)
{
int bytesRec = handler.Receive(bytes);
data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
if (data.IndexOf("<EOF>") > -1)
{
break;
}
}
// Show the data on the console.
label.Text = "Text received" + data;
// Echo the data back to the client.
byte[] msg = Encoding.ASCII.GetBytes(data);
handler.Send(msg);
handler.Shutdown(SocketShutdown.Both);
handler.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public Page2 ()
{
StartListening();
Title = "Sign in page";
InitializeComponent();
}
private void page2_click(object sender,EventArgs e)
{
Navigation.PushAsync(new Page1(), true);
}
}
}
Xaml File code:
Why is this?.and can you please provide an example of client mobile or server mobile socket

Answer 1

You are blocking the UI Thread with your StartListening call, since it has a infinite while loop.
The label you create in the while loop is never added as content on the page. Hence the text you add to it will never be shown. You already have a label defined with the name l on the page. In this case you could just use that to add text:
l.Text = "hello";
As commented, you should start your socket listening code on another thread to not block you UI. This could be as simple as writing Task.Run(() => StartListening());. Make sure you understand what this does and possibly how you cancel this Task again when navigating away from the page or during App lifecycle.

Answer 2

If you try to Connect from your mobile with the correct ip address and port number of the Listener when both devices are in the same LAN it should work. If one of the devices is behind a different LAN router/modem you won't be able to connect because the router will block all incoming connections unless you use a port routing mechanism like UPnP.