I wrote a chat application in C# WinForms. But if I close the client form (while this form is connected to the server form) and reopen the client form and try to reconnect, the client doesn't connect to the server..
How can I reconnect the client to the server if the application is closed and reopened?
(sorry for bad english)
Server:
public frmServer()
{
InitializeComponent();
textBox_Hostname.Text = GetLocalIPAddress();
Configuration Programmkonfiguration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
Port = Programmkonfiguration.AppSettings.Settings["Port"].Value;
textBox_Port.Text = Port;
toolStripStatusLabel_Serverstatus.Text = "deaktiviert";
toolStripStatusLabel_Serverstatus.ForeColor = Color.Red;
textBox_Output.Focus();
}
private string GetLocalIPAddress()
{
var host = Dns.GetHostEntry(Dns.GetHostName());
foreach (var ip in host.AddressList)
{
if (ip.AddressFamily == AddressFamily.InterNetwork)
{
return ip.ToString();
}
}
throw new Exception("No network adapters with an IPv4 address in the system!");
}
private void button_Send_Click(object sender, EventArgs e)
{
if (!(string.IsNullOrWhiteSpace(textBox_Output.Text)))
{
String s = "Server: " + textBox_Output.Text + Environment.NewLine;
textBox_Input.Text += s;
byte[] byteTime = Encoding.ASCII.GetBytes(s);
ns.Write(byteTime, 0, byteTime.Length);
textBox_Output.Clear();
}
}
public void DoWork()
{
byte[] bytes = new byte[1024];
while (true)
{
int bytesRead = ns.Read(bytes, 0, bytes.Length);
this.SetText(Encoding.ASCII.GetString(bytes, 0, bytesRead));
}
}
private void SetText(string text)
{
if (this.textBox_Input.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
this.textBox_Input.Text = this.textBox_Input.Text + text;
}
}
private void button_Starten_Click(object sender, EventArgs e)
{
IPAddress hostname = IPAddress.Parse(textBox_Hostname.Text);
int portNum = Convert.ToInt32(textBox_Port.Text);
listener = new TcpListener(hostname, portNum);
listener.Start();
Task TCPListener = new Task(() => AcceptTCP());
TCPListener.Start();
textBox_Input.Text += "Server gestartet." + Environment.NewLine;
button_Starten.Enabled = false;
toolStripStatusLabel_Serverstatus.Text = "aktiviert";
toolStripStatusLabel_Serverstatus.ForeColor = Color.Green;
}
private void AcceptTCP()
{
client = listener.AcceptTcpClient();
ns = client.GetStream();
Task Work = new Task(() => DoWork());
Work.Start();
}
private void textBox_Output_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Enter)
{
button_Send_Click(sender, e);
e.Handled = true;
textBox_Output.Focus();
}
}
}
Client:
public frmClient()
{
InitializeComponent();
Configuration Programmkonfiguration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
HostnameServer = Programmkonfiguration.AppSettings.Settings["HostnameServer"].Value;
Port = Programmkonfiguration.AppSettings.Settings["Port"].Value;
textBox_Hostname.Text = GetLocalIPAddress();
textBox_Port.Text = Port;
toolStripStatusLabel_Status.Text = " nicht verbunden";
toolStripStatusLabel_Status.ForeColor = Color.Red;
textBox_Output.Focus();
}
private string GetLocalIPAddress()
{
var host = Dns.GetHostEntry(HostnameServer);
foreach (var ip in host.AddressList)
{
if (ip.AddressFamily == AddressFamily.InterNetwork)
{
return ip.ToString();
}
}
throw new Exception("No network adapters with an IPv4 address in the system!");
}
private void button_Senden_Click(object sender, EventArgs e)
{
if (!(string.IsNullOrWhiteSpace(textBox_Output.Text)))
{
String s = "Client: " + textBox_Output.Text + Environment.NewLine;
textBox_Input.Text += s;
byte[] byteTime = Encoding.ASCII.GetBytes(s);
ns.Write(byteTime, 0, byteTime.Length);
textBox_Output.Clear();
}
}
public void DoWork()
{
byte[] bytes = new byte[1024];
while (true)
{
if (ns.DataAvailable)
{
int bytesRead = ns.Read(bytes, 0, bytes.Length);
this.SetText(Encoding.ASCII.GetString(bytes, 0, bytesRead));
}
}
}
private void SetText(string text)
{
if (this.textBox_Input.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
this.textBox_Input.Text = this.textBox_Input.Text + text;
}
}
private void button_Connect_Click(object sender, EventArgs e)
{
string hostName = textBox_Hostname.Text;
int portNum = Convert.ToInt32(textBox_Port.Text);
client = new TcpClient(hostName, portNum);
ns = client.GetStream();
Work = new Task(() => DoWork());
Work.Start();
textBox_Input.Text += "Verbindung hergestellt." + Environment.NewLine;
button_Connect.Enabled = false;
toolStripStatusLabel_Status.Text = "verbunden";
toolStripStatusLabel_Status.ForeColor = Color.Green;
}
private void textBox_Output_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Enter)
{
button_Senden_Click(sender, e);
e.Handled = true;
textBox_Output.Focus();
}
}
}
Each call to Accept on a listener socket accepts a single connection. At the moment, your server accepts a single connection request and then ignores the listener socket from that point onwards.
Normally, you'd want some form of "Accept loop" that continually calls Accept, sets up the server side resources for that connection and then loops back to call Accept again.
E.g. the trivial change is to do this:
private void AcceptTCP()
{
while(true)
{
client = listener.AcceptTcpClient();
ns = client.GetStream();
Task Work = new Task(() => DoWork());
Work.Start();
}
}
But now you really have to think about what happens to ns - what happens if/when you want a second client connected simultaneously? Having NetworkStream be a single shared instance variable within the server isn't going to scale well.
Normally, you'd want to create some form of simple class that represents each connection + your server specific information relating to that connection. E.g. it would contain the NetworkStream, the current "state" of this connection (if you have modes or states), possibly the buffers that were last passed to a Read call as/when you start going async with this work, etc.