using System;

using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.Xml.Linq;

using FlyOutMenu.Model;
using NetworkCommsDotNet;
using NetworkCommsDotNet.Connections;
using System.Net;
using NetworkCommsDotNet.Connections.TCP;

namespace FlyOutMenu
{
	[Activity (Label = "FlyInMenu", MainLauncher = true, Theme = "@android:style/Theme.Holo.Light.NoActionBar")]
    public class Login : Activity
	{
        string ip="192.168.43.155";
        int port=6003;
		protected override void OnCreate (Bundle bundle)
		{
			base.OnCreate (bundle);

			// Set our view from the "main" layout resource
			SetContentView (Resource.Layout.Login);

            Button btnLogin = FindViewById<Button>(Resource.Id.login);
            btnLogin.Click += new EventHandler(btnLogin_Click);
            TextView txtSheZhi = FindViewById<TextView>(Resource.Id.SheZhi);
            txtSheZhi.Click += new EventHandler(txtSheZhi_Click);

		}
        //Trigger when click the login button
        void btnLogin_Click(object sender, EventArgs e)
        {
            try
            { 
               ConnectionInfo info = new ConnectionInfo(ip, port);
               TCPConnection conn = TCPConnection.GetConnection(info);
               string i = conn.SendReceiveObject<string, string>("Message", "Re", 1000, "Hello word");
               Toast.MakeText(this, i, ToastLength.Long).Show();
            }
            catch (Exception ex)
            {
                Toast.MakeText(this, ex.ToString(), ToastLength.Long).Show();
            }

        }
    
	}
}

PC is already successfully received the “Hello word”.
When the PC terminal to send a return value back to the Android, but that such errors.

The same mistake:

NetworkCommsDotNet.ConnectionShutdownException: Remote end closed connection bef
ore data was successfully returned.
at NetworkCommsDotNet.Connections.Connection.SendReceiveObject[String,String]
(System.String sendingPacketTypeStr, System.String expectedReturnPacketTypeStr,
Int32 returnPacketTimeOutMilliSeconds, System.String sendObject, NetworkCommsDot
Net.SendReceiveOptions sendOptions, NetworkCommsDotNet.SendReceiveOptions receiv
eOptions, System.Int64& sentPacketSequenceNumber) [0x00000] in <filename unknown
>:0
at NetworkCommsDotNet.Connections.Connection.SendReceiveObject[String,String]
(System.String sendingPacketTypeStr, System.String expectedReturnPacketTypeStr,
Int32 returnPacketTimeOutMilliSeconds, System.String sendObject, NetworkCommsDot
Net.SendReceiveOptions sendOptions, NetworkCommsDotNet.SendReceiveOptions receiv
eOptions) [0x00000] in <filename unknown>:0
at NetworkCommsDotNet.Connections.Connection.SendReceiveObject[String,String]
(System.String sendingPacketTypeStr, System.String expectedReturnPacketTypeStr,
Int32 returnPacketTimeOutMilliSeconds, System.String sendObject) [0x00000] in <f
ilename unknown>:0
at FlyOutMenu.Login.btnLogin_Click (System.Object sender, System.EventArgs e)
[0x00000] in <filename unknown>:0