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Problem with sending and receiving in streams C# in textbox Windows Forms app

I managed to create a client server that communicate through forms.
I am able to display fist waiting and accepted messages.
My problem is when I'm writing to the stream and reading it on the other side the forms.
Here is where the sending and receiving happens on both programs:
Server-side code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net.Sockets;
using System.IO;
using System.Threading;
using System.Net;
using System.Diagnostics;
namespace serverApp
{
public partial class Form1 : Form
{
private static int connections = 0;
public Form1() { }
private void Form1_Load(object sender, EventArgs e)
{
}
private void CreateServer()
{
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream,
ProtocolType.Tcp);
IPEndPoint localEP = new IPEndPoint(IPAddress.Any, 9050);
server.Bind(localEP);
server.Listen(10);
serverTxtbox.AppendText("waiting for a client");
BackgroundWorker worker1 = new BackgroundWorker();
worker1.RunWorkerAsync(handlingFunction(server));
}
public object handlingFunction(Socket server)
{
while (true)
{
try
{
Socket client = server.Accept();
NetworkStream ns = new NetworkStream(client);
StreamReader reader = new StreamReader(ns);
StreamWriter writer = new StreamWriter(ns);
connections++;
serverTxtbox.AppendText("New client accepted: active connections
${connections}");
writer.WriteLine("Welcome to my server");
writer.Flush();
string input;
while (true)
{
input = reader.ReadLine();
if (input.Length == 0 || input.ToLower() == "exit")
break;
serverTxtbox.AppendText(input);
writer.WriteLine(input);
writer.Flush();
} //end of while
ns.Close();
//client.Close();
//connections--;
Console.WriteLine("Client disconnected: {0} active connections",
connections);
}
catch (Exception)
{
connections--;
Console.WriteLine("Client disconnected: {0} active connections", connections);
} //end of catch block
} // end of HandleConnection function
private void serverTxtbox_TextChanged(object sender, EventArgs e)
{
serverTxtbox.Clear();
}
private void button1_Click(object sender, EventArgs e)
{
//start button
try
{
CreateServer();
}
catch (Exception)
{
serverTxtbox.AppendText("Connection failed ..");
}
//client.Close();
//server.Shutdown();
}
}
}
Client-side code:
using System;
using System.ComponentModel;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Windows.Forms;
namespace app
{
public partial class Form1 : Form
{
Socket client;
NetworkStream stream;
StreamReader reader;
StreamWriter writer;
public Form1()
{
InitializeComponent();
}
private void sendBtn_Click(object sender, EventArgs e)
{
// writing to the server
handlfun();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private object ConnectionToServer(Socket client, IPEndPoint remoteEP)
{
//client.Connect(remoteEP);
try
{
client.Connect(remoteEP);
clientTextbox.Text = "Enter Message for Server <Enter to Stop >: ";
}
catch (SocketException e)
{
clientTextbox.AppendText("Unable to connect to server. ");
// clientTextbox.AppendText("e");
}
return client;
// Client.Shutdown(SocketShutdown.Both);
// Client.Close();
}
private void connectbtn_Click(object sender, EventArgs e)
{
client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint remoteEP = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9050);
BackgroundWorker worker1 = new BackgroundWorker();
worker1.RunWorkerAsync(ConnectionToServer(client, remoteEP));
}
public void handlfun()
{
stream = new NetworkStream(client);
reader = new StreamReader(stream);
writer = new StreamWriter(stream);
String input = clientTextbox.Text;
writer.WriteLine(input);
//clientTextbox.Text = input;
// String input = reader.ReadLine();
writer.Flush();
String line = null;
while (true)
{
clientTextbox.Text = "Enter Message for Server <Enter to Stop >: ";
line = clientTextbox.Text;
writer.WriteLine(line);
writer.Flush();
if (line.Length != 0)
{
line = "Echo: " + reader.ReadLine();
clientTextbox.Text = line;
}
}
}
}
}

C# TCP Application won't work

I'm making a simple chat application using TcpClient and TcpServer from System.Net.
I got everything working on my PC, the server communicates with the client and vice versa. But when I try to connect to the same server application using another PC (even on the same subnet as my PC) the thing doesn't work.
I've tried port-forwarding through my router, firewall and still nothing.
The Can you see me website says that the connection is being refused. Although!! Sometimes it says that the connection is timed out completely.
I am not sure what's wrong with my code or my PC, I would really appreciate some help from people that are more experienced in this area than I am.
Here is the configuration for the port forwarding in my router:
If you need the code for the client and the server, here they are:
P.S. I make the change to the client in the BeginConnect() part at the bottom in order to change the IP address that I'm connecting to
Client:
using System;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Net;
namespace TcpTest_Client_
{
public partial class Form1 : Form
{
TcpClient client;
IPAddress localIP = null;
bool connected = false;
public Form1()
{
InitializeComponent();
}
public void clientConnectCallback(IAsyncResult result)
{
try
{
client.EndConnect(result);
Log("Connected to " + client.Client.RemoteEndPoint);
connected = true;
NetworkStream clientStream = client.GetStream();
byte[] message = new byte[4096];
int bytesRead;
while (true)
{
bytesRead = 0;
try
{
//blocks until a client sends a message
bytesRead = clientStream.Read(message, 0, 4096);
}
catch (Exception ex)
{
//a socket error has occured
Log(ex.Message);
break;
}
if (bytesRead == 0)
{
//the client has disconnected from the server
Log("Server on has disconnected");
break;
}
//message has successfully been received
UTF8Encoding encoder = new UTF8Encoding();
string bufferincmessage = encoder.GetString(message, 0, bytesRead);
Log("Server: " + bufferincmessage);
}
}
catch (Exception ex)
{
Log(ex.Message);
}
}
public void Log(string msg)
{
richTextBox1.BeginInvoke(new Action(
() =>
{
richTextBox1.Text += msg + "\n";
}));
}
private void Form1_Load(object sender, EventArgs e)
{
foreach (IPAddress addr in Dns.GetHostAddresses(Dns.GetHostName()))
{
if (addr.AddressFamily == AddressFamily.InterNetwork)
{
localIP = addr;
break;
}
}
client = new TcpClient(AddressFamily.InterNetwork);
}
private void button2_Click(object sender, EventArgs e)
{
try
{
client.BeginConnect(IPAddress.Parse("109.252.107.144"), 1234, clientConnectCallback, client);
}
catch (Exception ex)
{
Log(ex.Message);
}
}
private void button1_Click(object sender, EventArgs e)
{
if (connected)
{
UTF8Encoding encoder = new UTF8Encoding();
NetworkStream clientStream = client.GetStream();
byte[] stringToSend = new byte[richTextBox2.Text.Length];
stringToSend = encoder.GetBytes(richTextBox2.Text);
clientStream.Write(stringToSend, 0, stringToSend.Length);
}
}
}
}
Server:
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace TcpTest
{
public partial class Form1 : Form
{
private TcpListener server;
private List<Thread> clientThreads = null;
public Thread MainThread;
public Form1()
{
InitializeComponent();
}
public void Log(string msg)
{
richTextBox1.BeginInvoke(new Action(
() =>
{
richTextBox1.Text += msg + "\n";
}));
}
public static string bufferincmessage;
public void AcceptSocketPackets(object client)
{
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
byte[] message = new byte[4096];
int bytesRead;
while (true)
{
bytesRead = 0;
try
{
//blocks until a client sends a message
bytesRead = clientStream.Read(message, 0, 4096);
}
catch (Exception ex)
{
//a socket error has occured
Log(ex.Message);
break;
}
if (bytesRead == 0)
{
//the client has disconnected from the server
Log("Client on " + tcpClient.Client.RemoteEndPoint + " has disconnected from the server");
break;
}
//message has successfully been received
UTF8Encoding encoder = new UTF8Encoding();
bufferincmessage = encoder.GetString(message, 0, bytesRead);
Log("Client from " + tcpClient.Client.RemoteEndPoint + ": " + bufferincmessage);
string stringToSend = "You sent me: " + bufferincmessage;
byte[] messageToSend = new byte[stringToSend.Length];
messageToSend = encoder.GetBytes(stringToSend);
clientStream.Write(messageToSend, 0, messageToSend.Length);
}
}
public void SocketAcceptCallback(IAsyncResult result)
{
TcpClient newClient = server.EndAcceptTcpClient(result);
Log("Accepted client on " + newClient.Client.RemoteEndPoint);
clientThreads.Add(new Thread(new ParameterizedThreadStart(AcceptSocketPackets)));
clientThreads[clientThreads.Count - 1].Start(newClient);
server.BeginAcceptTcpClient(SocketAcceptCallback, server);
}
private void Form1_Load(object sender, EventArgs e)
{
MainThread = Thread.CurrentThread;
clientThreads = new List<Thread>();
try
{
IPAddress localIP = null;
foreach (IPAddress addr in Dns.GetHostAddresses(Dns.GetHostName()))
{
if (addr.AddressFamily == AddressFamily.InterNetwork)
{
localIP = addr;
break;
}
}
localIP = IPAddress.Any;
// could also use this:
// server = new TcpListener(new IPEndPoint(IPAddress.Any, 1234));
server = new TcpListener(new IPEndPoint(localIP, 1234));
Log("Starting server on " + localIP + ":1234");
server.Start(6);
server.BeginAcceptTcpClient(SocketAcceptCallback, server);
Log("Started server on " + localIP + ":1234");
}
catch (Exception ex)
{
Log(ex.Message);
}
}
}
}

C++ is giving me problems like that. Try creating another project, paste the server code and build it as Release x86. If you change the build target and our problem is the same, windows firewall, even when turned off, won't allow the server or the client to run without any exception. If it doesn't work I might not know the answer.

data from gps sometimes changed to unreadable format

I am getting data from avl system as you can see with this format :
*HQ,4106016320,V1,090458,A,5257.4318,N,15840.4221,E,000.00,000,101115,FFFFFBFF,250,01,0,0,5#
As you can see the data that i get from the gps is :
As you can see in some lines the data is unreadable .why this problem happened?
My server that gets the data is like this :
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace smartparckingHandlerServer
{
public partial class Form1 : Form
{
public AsyncCallback pfnWorkerCallBack;
private Socket m_mainSocket;
private Socket[] m_workerSocket = new Socket[25];
private int m_clientCount = 0;
private string ipaddress;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
startfun();
}
public void startfun()
{
try
{
// DrawMapPersian();
ipaddress = "127.0.0.1";
// Check the port value
string portStr = "5000";
int port = System.Convert.ToInt32(portStr);
// Create the listening socket...
m_mainSocket = new Socket(AddressFamily.InterNetwork,
SocketType.Stream,
ProtocolType.Tcp);
IPEndPoint ipLocal = new IPEndPoint(IPAddress.Any, port);
// Bind to local IP Address...
m_mainSocket.Bind(ipLocal);
listBox1.Items.Add("Server Started...");
// Start listening...
m_mainSocket.Listen(20);
listBox1.Items.Add("Server Listening for ...");
// Create the call back for any client connections...
m_mainSocket.BeginAccept(new AsyncCallback(OnClientConnect), null);
}
catch (Exception qqq)
{
using (StreamWriter writer =
new StreamWriter(#"f:\a.txt"))
{
writer.Write(qqq.Message);
}
}
}
public void OnClientConnect(IAsyncResult asyn)
{
try
{
// Here we complete/end the BeginAccept() asynchronous call
// by calling EndAccept() - which returns the reference to
// a new Socket object
m_workerSocket[m_clientCount] = m_mainSocket.EndAccept(asyn);
// Let the worker Socket do the further processing for the
// just connected client
WaitForData(m_workerSocket[m_clientCount]);
// Now increment the client count
++m_clientCount;
// Display this client connection as a status message on the GUI
String str = String.Format("Client # {0} connected", m_clientCount);
// Since the main Socket is now free, it can go back and wait for
// other clients who are attempting to connect
m_mainSocket.BeginAccept(new AsyncCallback(OnClientConnect), null);
using (StreamWriter writer =
new StreamWriter(#"f:\con.txt"))
{
writer.Write("connect to client");
}
}
catch (Exception qqq)
{
using (StreamWriter writer =
new StreamWriter(#"f:\a.txt"))
{
writer.Write(qqq.Message);
}
}
}
public class SocketPacket
{
public System.Net.Sockets.Socket m_currentSocket;
public byte[] dataBuffer = new byte[200];
}
public void WaitForData(System.Net.Sockets.Socket soc)
{
try
{
if (pfnWorkerCallBack == null)
{
// Specify the call back function which is to be
// invoked when there is any write activity by the
// connected client
pfnWorkerCallBack = new AsyncCallback(OnDataReceived);
}
SocketPacket theSocPkt = new SocketPacket();
theSocPkt.m_currentSocket = soc;
// Start receiving any data written by the connected client
// asynchronously
soc.BeginReceive(theSocPkt.dataBuffer, 0,
theSocPkt.dataBuffer.Length,
SocketFlags.None,
pfnWorkerCallBack,
theSocPkt);
}
catch (Exception qqq)
{
using (StreamWriter writer =
new StreamWriter(#"f:\a.txt"))
{
writer.Write(qqq.Message);
}
}
}
public void OnDataReceived(IAsyncResult asyn)
{
try
{
SocketPacket socketData = (SocketPacket)asyn.AsyncState;
int iRx = 0;
// Complete the BeginReceive() asynchronous call by EndReceive() method
// which will return the number of characters written to the stream
// by the client
iRx = socketData.m_currentSocket.EndReceive(asyn);
string res = GetParameters(socketData.dataBuffer);
Console.WriteLine(res.ToString());
//char[] chars = new char[iRx + 1];
//System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
//int charLen = d.GetChars(socketData.dataBuffer,
// 0, iRx, chars, 0);
//System.String szData = new System.String(chars);
this.Invoke(new MethodInvoker(delegate ()
{
listBox1.Items.Add("clinet's data:" + res);
}));
// Continue the waiting for data on the Socket
WaitForData(socketData.m_currentSocket);
//socketData = null;
}
catch (ObjectDisposedException)
{
System.Diagnostics.Debugger.Log(0, "1", "\nOnDataReceived: Socket has been closed\n");
}
catch (SocketException se)
{
}
catch (Exception qqq)
{
using (StreamWriter writer =
new StreamWriter(#"f:\a.txt"))
{
writer.Write(qqq.Message);
}
}
}
public string GetParameters(byte[] buf)
{
string result = System.Text.Encoding.ASCII.GetString(buf);
return result;
}
}
}
when i move the GPS it returns unreadable data.why?

It's a longshot, but try changing
string result = System.Text.Encoding.ASCII.GetString(buf);
to
string result = System.Text.Encoding.UTF8.GetString(buf);
or
string result = System.Text.Encoding.Default.GetString(buf);

Socket Programming - A connection attempt failed Exception

Am new to socket programming and am creating a chat application.As like other applications whenever i press enter in a chat window it should send the chat to a particular user.Am maintaining a DB for all users along with their IPAddresses.So whenever i select a user for sending chat it should send to the corresponding IPAddress.As of now am trying to send chat to my own machine(so i hard coded the IPAddress of my machine).But am getting an exception when i try to send my code to my IPAddress.Can anyone please help me out.
My code for socket programming is this
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
using System.IO;
using System.Net.Sockets;
namespace Ping
{
class SocketProgramming
{
//Socket m_socWorker;
public AsyncCallback pfnWorkerCallBack;
public Socket m_socListener;
public Socket m_socWorker;
public void sendChat(IPAddress toMessengerIP)
{
try
{
//create a new client socket ...
m_socWorker = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
String szIPSelected = toMessengerIP.ToString();
String szPort = "7777";
int alPort = System.Convert.ToInt16(szPort, 10);
System.Net.IPAddress remoteIPAddress = System.Net.IPAddress.Parse(szIPSelected);
System.Net.IPEndPoint remoteEndPoint = new System.Net.IPEndPoint(remoteIPAddress, alPort);
// receive();
m_socWorker.Connect(remoteEndPoint);
//Send data
Object objData =(object)"hi dhivi";
byte[] byData = System.Text.Encoding.ASCII.GetBytes(objData.ToString());
m_socWorker.Send(byData);
}
catch (System.Net.Sockets.SocketException se)
{
//MessageBox.Show(se.Message);
Console.Out.Write(se.Message);
}
}
public void receive()
{
try
{
//create the listening socket...
m_socListener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipLocal = new IPEndPoint(IPAddress.Any, 7777);
//bind to local IP Address...
m_socListener.Bind(ipLocal);
//start listening...
m_socListener.Listen(4);
// create the call back for any client connections...
m_socListener.BeginAccept(new AsyncCallback(OnClientConnect), null);
//cmdListen.Enabled = false;
}
catch (SocketException se)
{
Console.Out.Write(se.Message);
}
}
public void OnClientConnect(IAsyncResult asyn)
{
try
{
m_socWorker = m_socListener.EndAccept(asyn);
WaitForData(m_socWorker);
}
catch (ObjectDisposedException)
{
System.Diagnostics.Debugger.Log(0, "1", "\n OnClientConnection: Socket has been closed\n");
}
catch (SocketException se)
{
Console.Out.Write(se.Message);
}
}
public class CSocketPacket
{
public System.Net.Sockets.Socket thisSocket;
public byte[] dataBuffer = new byte[1];
}
public void WaitForData(System.Net.Sockets.Socket soc)
{
try
{
//if (pfnWorkerCallBack == null)
//{
// pfnWorkerCallBack = new AsyncCallback(OnDataReceived);
//}
CSocketPacket theSocPkt = new CSocketPacket();
theSocPkt.thisSocket = soc;
// now start to listen for any data...
soc.BeginReceive(theSocPkt.dataBuffer, 0, theSocPkt.dataBuffer.Length, SocketFlags.None, pfnWorkerCallBack, theSocPkt);
}
catch (SocketException se)
{
Console.Out.Write(se.Message);
}
}
}
}
And whenever the users clicks the enter button it should call the sendChat() method.
private void txt_Userinput_KeyDown_1(object sender, KeyEventArgs e)
{
Window parentWindow = Window.GetWindow(this);
TabItem tb = (TabItem)this.Parent;
string user = tb.Header.ToString();
if (e.Key == Key.Return)
{
richtxtbox_chatwindow.AppendText(Environment.NewLine + user + " : " + txt_Userinput.Text);
DBCoding dbObject = new DBCoding();
SocketProgramming socketObj = new SocketProgramming();
socketObj.sendChat(IPAddress.Parse("192.168.15.41"));
}
else { return; }
}
To get ipaddress of the user
public IPAddress getIP()
{
String direction = "";
WebRequest request = WebRequest.Create("http://checkip.dyndns.org/");
using (WebResponse response = request.GetResponse())
using (StreamReader stream = new StreamReader(response.GetResponseStream()))
{
direction = stream.ReadToEnd();
}
//Search for the ip in the html
int first = direction.IndexOf("Address: ") + 9;
int last = direction.LastIndexOf("</body>");
direction = direction.Substring(first, last - first);
IPAddress ip = IPAddress.Parse(direction);
return ip;
}

You never seem to be calling your receive method. If your application never starts listening, no one will ever be able to connect. If you've tried that, and is getting an exception, post that and we'll go from there.

SocketException when connecting to server

I am running both client and server on the same machine.
Does any 1 know the error stated above?
server
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Net.Sockets;
using System.IO;
using System.Net;
namespace Server
{
public partial class Server : Form
{
private Socket connection;
private Thread readThread;
private NetworkStream socketStream;
private BinaryWriter writer;
private BinaryReader reader;
//default constructor
public Server()
{
InitializeComponent();
//create a new thread from server
readThread = new Thread(new ThreadStart(RunServer));
readThread.Start();
}
protected void Server_Closing(object sender, CancelEventArgs e)
{
System.Environment.Exit(System.Environment.ExitCode);
}
//sends the text typed at the server to the client
protected void inputText_KeyDown(object sender, KeyEventArgs e)
{
// send the text to client
try
{
if (e.KeyCode == Keys.Enter && connection != null)
{
writer.Write("Server>>> " + inputText.Text);
displayText.Text +=
"\r\nSERVER>>> " + inputText.Text;
//if user at server enter terminate
//disconnect the connection to the client
if (inputText.Text == "TERMINATE")
connection.Close();
inputText.Clear();
}
}
catch (SocketException)
{
displayText.Text += "\nError writing object";
}
}//inputTextBox_KeyDown
// allow client to connect & display the text it sends
public void RunServer()
{
TcpListener listener;
int counter = 1;
//wait for a client connection & display the text client sends
try
{
//step 1: create TcpListener
IPAddress ipAddress = Dns.Resolve("localhost").AddressList[0];
TcpListener tcplistener = new TcpListener(ipAddress, 9000);
//step 2: TcpListener waits for connection request
tcplistener.Start();
//step 3: establish connection upon client request
while (true)
{
displayText.Text = "waiting for connection\r\n";
// accept incoming connection
connection = tcplistener.AcceptSocket();
//create NetworkStream object associated with socket
socketStream = new NetworkStream(connection);
//create objects for transferring data across stream
writer = new BinaryWriter(socketStream);
reader = new BinaryReader(socketStream);
displayText.Text += "Connection " + counter + " received.\r\n ";
//inform client connection was successful
writer.Write("SERVER>>> Connection successful");
inputText.ReadOnly = false;
string theReply = "";
// step 4: read string data sent from client
do
{
try
{
//read the string sent to the server
theReply = reader.ReadString();
// display the message
displayText.Text += "\r\n" + theReply;
}
// handle the exception if error reading data
catch (Exception)
{
break;
}
} while (theReply != "CLIENT>>> TERMINATE" && connection.Connected);
displayText.Text +=
"\r\nUser terminated connection";
// step 5: close connection
inputText.ReadOnly = true;
writer.Close();
reader.Close();
socketStream.Close();
connection.Close();
++counter;
}
} //end try
catch (Exception error)
{
MessageBox.Show(error.ToString());
}
}
}// end method runserver
}// end class server
client
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Net.Sockets;
using System.IO;
using System.Net;
namespace Client
{
public partial class Client : Form
{
private NetworkStream output;
private BinaryWriter writer;
private BinaryReader reader;
private string message = "";
private Thread readThread;
//default constructor
public Client()
{
InitializeComponent();
readThread = new Thread(new ThreadStart(RunClient));
readThread.Start();
}
protected void Client_Closing(
object sender, CancelEventArgs e)
{
System.Environment.Exit(System.Environment.ExitCode);
}
//sends the text user typed to server
protected void inputText_KeyDown(
object sender, KeyEventArgs e)
{
try
{
if (e.KeyCode == Keys.Enter)
{
writer.Write("CLIENT>>> " + inputText.Text);
displayText.Text +=
"\r\nCLIENT>>> " + inputText.Text;
inputText.Clear();
}
}
catch (SocketException ioe)
{
displayText.Text += "\nError writing object";
}
}//end method inputText_KeyDown
//connect to server & display server-generated text
public void RunClient()
{
TcpClient client;
//instantiate TcpClient for sending data to server
try
{
displayText.Text += "Attempting connection\r\n";
//step1: create TcpClient for sending data to server
client = new TcpClient();
client.Connect("localhost", 9000);
//step2: get NetworkStream associated with TcpClient
output = client.GetStream();
//create objects for writing & reading across stream
writer = new BinaryWriter(output);
reader = new BinaryReader(output);
displayText.Text += "\r\nGot I/O streams\r\n";
inputText.ReadOnly = false;
//loop until server terminate
do
{
//step3: processing phase
try
{
//read from server
message = reader.ReadString();
displayText.Text += "\r\n" + message;
}
//handle exception if error in reading server data
catch (Exception)
{
System.Environment.Exit(System.Environment.ExitCode);
}
} while (message != "SERVER>>> TERMINATE");
displayText.Text += "\r\nClosing connection.\r\n";
//step4: close connection
writer.Close();
reader.Close();
output.Close();
client.Close();
Application.Exit();
}
catch (Exception error)
{
MessageBox.Show(error.ToString());
}
}
}
}

It is probably your firewall acting up. Try connecting to something like www.google.com on TCP 80 just to see if you can actually connect.

Are you using a newer version of Windows? It's possible that you're only listening on IPv4, but "localhost" is resolving to an IPv6 address and it's not finding it. Try connecting to "127.0.0.1" instead of localhost and see if the result changes.

mk,
I'd tcplistener/tcpclient for simple applications . . .
TheEruditeTroglodyte

If you use that constructor with TCPListener then it will let the underlying service provider pick a network address, which probably won't be 'localhost'. You're probably listening on your LAN/WLAN card instead of localhost.
Take a look at the MSDN page for TCPListener, the sample there shows how to use a different constructor, look at the other constructors for more samples.
Here's one way:
IPAddress ipAddress = Dns.Resolve("localhost").AddressList[0];
TcpListener tcpListener = new TcpListener(ipAddress, 9000);