.NET sample client
This project example shows how a client for the PLC TCP/IP server can be realised by writing a .NET4.0 application using C#.
This sample client makes use of the .NET libraries System.Net and System.Net.Sockets which enable a programmer easy access to socket functionalities. By pressing the button "Enable", the application attempts to cyclically (depending on the value of TIMERTICK in [ms]) establish a connection with the server. If successful, a string with a maximum length of 255 characters can be sent to the server via the "Send" button. The server will then take this string and send it back to the client. On the server side, the connection is closed automatically if the server was unable to receive new data from the client within a defined period, as specified by PLCPRJ_RECEIVE_TIMEOUT in the server sample - by default 50 seconds.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
/* ##########################################################################################
* This sample TCP/IP client connects to a TCP/IP-Server, sends a message and waits for the
* response. It is being delivered together with our TCP-Sample, which implements an echo server
* in PLC.
* ########################################################################################## */
namespace TcpIpServer_SampleClient
{
public partial class Form1 : Form
{
/* ##########################################################################################
* Constants
* ########################################################################################## */
private const int RCVBUFFERSIZE = 256; // buffer size for receive buffer
private const string DEFAULTIP = "127.0.0.1";
private const string DEFAULTPORT = "200";
private const int TIMERTICK = 100;
/* ##########################################################################################
* Global variables
* ########################################################################################## */
private static bool _isConnected; // signals whether socket connection is active or not
private static Socket _socket; // object used for socket connection to TCP/IP-Server
private static IPEndPoint _ipAddress; // contains IP address as entered in text field
private static byte[] _rcvBuffer; // receive buffer used for receiving response from TCP/IP-Server
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
_rcvBuffer = newbyte[RCVBUFFERSIZE];
/* ##########################################################################################
* Prepare GUI
* ########################################################################################## */
cmd_send.Enabled = false;
cmd_enable.Enabled = true;
cmd_disable.Enabled = false;
rtb_rcvMsg.Enabled = false;
rtb_sendMsg.Enabled = false;
rtb_statMsg.Enabled = false;
txt_host.Text = DEFAULTIP;
txt_port.Text = DEFAULTPORT;
timer1.Enabled = false;
timer1.Interval = TIMERTICK;
_isConnected = false;
}
private void cmd_enable_Click(object sender, EventArgs e)
{
/* ##########################################################################################
* Parse IP address in text field, start background timer and prepare GUI
* ########################################################################################## */
try
{
_ipAddress = newIPEndPoint(IPAddress.Parse(txt_host.Text), Convert.ToInt32(txt_port.Text));
timer1.Enabled = true;
cmd_enable.Enabled = false;
cmd_disable.Enabled = true;
rtb_sendMsg.Enabled = true;
cmd_send.Enabled = true;
txt_host.Enabled = false;
txt_port.Enabled = false;
rtb_sendMsg.Focus();
}
catch (Exception ex)
{
MessageBox.Show("Could not parse entered IP address. Please check spelling and retry. " + ex);
}
}
/* ##########################################################################################
* Timer periodically checks for connection to TCP/IP-Server and reestablishes if not connected
* ########################################################################################## */
private void timer1_Tick(object sender, EventArgs e)
{
if (!_isConnected)
connect();
}
private void connect()
{
/* ##########################################################################################
* Connect to TCP/IP-Server using the IP address specified in the text field
* ########################################################################################## */
try
{
_socket = newSocket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
_socket.Connect(_ipAddress);
_isConnected = true;
if (_socket.Connected)
rtb_statMsg.AppendText(DateTime.Now.ToString() + ": Connectection to host established!\n");
else
rtb_statMsg.AppendText(DateTime.Now.ToString() + ": A connection to the host could not be established!\n");
}
catch (Exception ex)
{
MessageBox.Show("An error occured while establishing a connection to the server: " + ex);
}
}
private void cmd_send_Click(object sender, EventArgs e)
{
/* ##########################################################################################
* Read message from text field and prepare send buffer, which is a byte[] array. The last
* character in the buffer needs to be a termination character, so that the TCP/IP-Server knows
* when the TCP stream ends. In this case, the termination character is '0'.
* ########################################################################################## */
ASCIIEncoding enc = new ASCIIEncoding();
byte[] tempBuffer = enc.GetBytes(rtb_sendMsg.Text);
byte[] sendBuffer = new byte[tempBuffer.Length + 1];
for (int i = 0; i < tempBuffer.Length; i++)
sendBuffer[i] = tempBuffer[i];
sendBuffer[tempBuffer.Length] = 0;
/* ##########################################################################################
* Send buffer content via TCP/IP connection
* ########################################################################################## */
try
{
int send = _socket.Send(sendBuffer);
if (send == 0)
throw new Exception();
else
{
/* ##########################################################################################
* As the TCP/IP-Server returns a message, receive this message and store content in receive buffer.
* When message receive is complete, show the received message in text field.
* ########################################################################################## */
rtb_statMsg.AppendText(DateTime.Now.ToString() + ": Message successfully sent!\n");
IAsyncResult asynRes = _socket.BeginReceive(_rcvBuffer, 0, 256, SocketFlags.None, null, null);
if (asynRes.AsyncWaitHandle.WaitOne())
{
int res = _socket.EndReceive(asynRes);
char[] resChars = newchar[res + 1];
Decoder d = Encoding.UTF8.GetDecoder();
int charLength = d.GetChars(_rcvBuffer, 0, res, resChars, 0, true);
String result = newString(resChars);
rtb_rcvMsg.AppendText("\n" + DateTime.Now.ToString() + ": " + result);
rtb_sendMsg.Clear();
}
}
}
catch (Exception ex)
{
MessageBox.Show("An error occured while sending the message: " + ex);
}
}
private void cmd_disable_Click(object sender, EventArgs e)
{
/* ##########################################################################################
* Disconnect from TCP/IP-Server, stop the timer and prepare GUI
* ########################################################################################## */
timer1.Enabled = false;
_socket.Disconnect(true);
if (!_socket.Connected)
{
_isConnected = false;
cmd_disable.Enabled = false;
cmd_enable.Enabled = true;
txt_host.Enabled = true;
txt_port.Enabled = true;
rtb_sendMsg.Enabled = false;
cmd_send.Enabled = false;
rtb_statMsg.AppendText(DateTime.Now.ToString() + ": Connectection to host closed!\n");
rtb_rcvMsg.Clear();
rtb_statMsg.Clear();
}
}
}
}