C#

private void Form1_Load(object sender, EventArgs e)
       {
           //Set up socket
           sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
           sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

           //Get user IP
           txtLocalIP.Text = GetLocalIP();
           txtRemoteIP.Text = GetLocalIP();
       }


       private string GetLocalIP()
       {
           IPHostEntry host;
           host = Dns.GetHostEntry(Dns.GetHostName());
           foreach (IPAddress ip in host.AddressList)
           {
               if (ip.AddressFamily == AddressFamily.InterNetwork)
                   return ip.ToString();
           }
           return "127.0.0.1";
       }

       private void MessageCallBack(IAsyncResult aResult)
       {
           try
           {
               byte[] receivedData = new byte[1500];
               receivedData = (byte[])aResult.AsyncState;

               //Converting byte{] to string
               ASCIIEncoding aEncoding = new ASCIIEncoding();
               string receivedMessage = aEncoding.GetString(receivedData);

               //Adding this messegage into ListBox
               listMessage.Items.Add("Friend: " + receivedMessage);

               buffer = new byte[1500];
               sck.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref epRemote, new AsyncCallback(MessageCallBack), buffer);
           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.ToString());
           }
       }


       private void btnConnect_Click(object sender, EventArgs e)
       {
           //Binding socket
           epLocal = new IPEndPoint(IPAddress.Parse(txtLocalIP.Text), Convert.ToInt32(txtLocalPort.Text));
           sck.Bind(epLocal);

           //Connecting to remote IP
           epRemote = new IPEndPoint(IPAddress.Parse(txtRemoteIP.Text), Convert.ToInt32(txtRemotePort.Text));
           sck.Connect(epRemote);

           //Listen to specific port
           buffer = new byte[1500];
           sck.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref epRemote, new AsyncCallback(MessageCallBack), buffer);
       }

       private void btnSend_Click(object sender, EventArgs e)
       {
           //Convert string message to byte[]
           ASCIIEncoding aEncoding = new ASCIIEncoding();
           byte[] sendingMessage = new byte[1500];
           sendingMessage = aEncoding.GetBytes(txtMessage.Text);

           //Sending the Encoded message
           sck.Send(sendingMessage);

           //Adding to the ListBox
           listMessage.Items.Add("Me: " + txtMessage.Text);
           txtMessage.Text = "";
       }

int System.Windows.Forms.ListBox.ObjectCollection.Add(object)' has the wrong return type	

larsp777 wrote:

int System.Windows.Forms.ListBox.ObjectCollection.Add(object)' has the wrong return type

Invoke((Func<object, int>)listMessage.Items.Add, "Friend: " + receivedMessage);

larsp777 wrote:

listMessage.Items.Add("Friend: " + receivedMessage);

Invoke((Func<object, int>)listMessage.Items.Add, "Friend: " + receivedMessage);