C#

using System;
using System.Collections;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace mgMapsServer.Classes
{

    enum Command
    {
        Login,      //Log into the server
        Logout,     //Logout of the server
        callLog,    //Sends Call Log ID
        heartbeat,
        Reset,      //Command to Reset All Connections
        Null        //No command

    }

    public class TCPConnector
    {
        //The ClientInfo structure holds 
        //the required information about every
        //client connected to the server
        struct ClientInfo
        {
            //Socket of the client
            public Socket socket;
            //Name by which the user logged into the chat room
            public string strName;
        }
        struct HBInfo
        {
            public Socket socket;
            public int index;
        }

        //The collection of all clients logged 
        //into the room (an array of type ClientInfo)
        ArrayList clientList;

        //The main socket on which the server listens to the clients
        Socket serverSocket;

        //Heartbeat Container
        ArrayList HeartbeatList;

        byte[] byteData = new byte[1024];

        public TCPConnector()
        {
            clientList = new ArrayList();
            HeartbeatList = new ArrayList();

            try
            {
                serverSocket = new Socket(AddressFamily.InterNetwork,
                                          SocketType.Stream,
                                          ProtocolType.Tcp);


                IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Any, Convert.ToInt32(Library.sqlVars("serverPort")));

                //Bind and listen on the given address
                serverSocket.Bind(ipEndPoint);
                serverSocket.Listen(4);

                //Accept the incoming clients
                serverSocket.BeginAccept(new AsyncCallback(OnAccept), null);
				\*Logging Code*\
            }
            catch (Exception ex) { \*Logging Code*\ }
            }
        }



        private void OnAccept(IAsyncResult ar)
        {
            try
            {
                Socket clientSocket = serverSocket.EndAccept(ar);

                //Start listening for more clients
                serverSocket.BeginAccept(new AsyncCallback(OnAccept), null);

                //Once the client connects then start 
                //receiving the commands from her
                clientSocket.BeginReceive(byteData, 0,
                    byteData.Length, SocketFlags.None,
                    new AsyncCallback(OnReceive), clientSocket);
            }
            catch (Exception ex)  { \*Logging Code*\ }
        }



        private void OnReceive(IAsyncResult ar)
        {
            try
            {
                Socket clientSocket = (Socket)ar.AsyncState;
                clientSocket.EndReceive(ar);

                //Transform the array of bytes received from the user into an
                //intelligent form of object Data
                Data msgReceived = new Data(byteData);

                //We will send this object in response the users request
                Data msgToSend = new Data();

                //byte[] message;

                //If the message is to login, logout, or simple text message
                //then when send to others the type of the message remains the same
                msgToSend.cmdCommand = msgReceived.cmdCommand;
                msgToSend.strName = msgReceived.strName;

                switch (msgReceived.cmdCommand)
                {
                    case Command.heartbeat:

                        break;
                    case Command.Reset:
                        \*Logging Code*\
                        int rIndex = 0;
                        foreach (ClientInfo client in clientList)
                        {
                            clientList.RemoveAt(rIndex);
                            ++rIndex;
                        }
                        break;

                    case Command.Login:

                        //When a user logs in to the server then we add her to our
                        //list of clients

                        ClientInfo clientInfo = new ClientInfo();
                        clientInfo.socket = clientSocket;
                        clientInfo.strName = msgReceived.strName;

                        clientList.Add(clientInfo);

                        //Set the text of the message that we will broadcast to all users
                        msgToSend.strMessage = "<<<" + msgReceived.strName + " has Connected to the Server>>>";
                        break;

                    case Command.Logout:

                        //When a user wants to log out of the server then we search for her 
                        //in the list of clients and close the corresponding connection

                        int nIndex = 0;
                        foreach (ClientInfo client in clientList)
                        {
                            if (client.socket == clientSocket)
                            {
                                clientList.RemoveAt(nIndex);
                                break;
                            }
                            ++nIndex;
                        }

                        clientSocket.Close();

                        msgToSend.strMessage = "<<<" + msgReceived.strName + " has Disconnected from the server>>>";
                        break;
                }

                if ((msgReceived.cmdCommand != Command.heartbeat) || (msgReceived.cmdCommand != Command.heartbeat))
                {
                     \*Logging Code*\
                }
                if (msgReceived.cmdCommand != Command.Logout) { clientSocket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None, new AsyncCallback(OnReceive), clientSocket); }
            }
            catch (Exception ex)  { \*Logging Code*\ }
        }

        public string callLogIDSender
        {
            get { return null; }
            set { SendcallLogID(value); }
        }

        public void SendcallLogID(string ID)
        {
            try
            {
                Data msgToSend = new Data();
                byte[] message;
                msgToSend.cmdCommand = Command.callLog;
                msgToSend.strMessage = ID;
                message = msgToSend.ToByte();

				\*Logging Code*\
		
                foreach (ClientInfo clientInfo in clientList)
                {
                    clientInfo.socket.BeginSend(message, 0, message.Length, SocketFlags.None,
                        new AsyncCallback(OnSend), clientInfo.socket);
                }
            }
            catch (Exception ex) { \*Logging Code*\ }
        }

        public void sendHeartBeat()
        {
            try
            {
                Data msgToSend = new Data();
                byte[] message;
                msgToSend.cmdCommand = Command.heartbeat;
                msgToSend.strMessage = null;
                message = msgToSend.ToByte();
                int nIndex = 0;
                foreach (ClientInfo clientInfo in clientList)
                {
                    HBInfo tempHB = new HBInfo();
                    tempHB.index = nIndex;
                    tempHB.socket = clientInfo.socket;
                    HeartbeatList.Add(tempHB);
                    clientInfo.socket.BeginSend(message, 0, message.Length, SocketFlags.None,
                    new AsyncCallback(OnSend), clientInfo.socket);
                    
                    ++nIndex;
                       
                }
            }
            catch (Exception e) { \*Logging Code*\ }
        }

        public void OnSend(IAsyncResult ar)
        {
            try
            {
                Socket client = (Socket)ar.AsyncState;
                client.EndSend(ar);
            }
            catch (Exception ex) 
            {
                \\Logging Code
            }
        }
    }

    //The data structure by which the server and the client interact with 
    //each other
    class Data
    {
        //Default constructor
        public Data()
        {
            this.cmdCommand = Command.Null;
            this.strMessage = null;
            this.strName = null;
        }

        //Converts the bytes into an object of type Data
        public Data(byte[] data)
        {
            //The first four bytes are for the Command
            this.cmdCommand = (Command)BitConverter.ToInt32(data, 0);

            //The next four store the length of the name
            int nameLen = BitConverter.ToInt32(data, 4);

            //The next four store the length of the message
            int msgLen = BitConverter.ToInt32(data, 8);

            //This check makes sure that strName has been passed in the array of bytes
            if (nameLen > 0)
                this.strName = Encoding.UTF8.GetString(data, 12, nameLen);
            else
                this.strName = null;

            //This checks for a null message field
            if (msgLen > 0)
                this.strMessage = Encoding.UTF8.GetString(data, 12 + nameLen, msgLen);
            else
                this.strMessage = null;
        }

        //Converts the Data structure into an array of bytes
        public byte[] ToByte()
        {
            List<byte> result = new List<byte>();

            //First four are for the Command
            result.AddRange(BitConverter.GetBytes((int)cmdCommand));

            //Add the length of the name
            if (strName != null)
                result.AddRange(BitConverter.GetBytes(strName.Length));
            else
                result.AddRange(BitConverter.GetBytes(0));

            //Length of the message
            if (strMessage != null)
                result.AddRange(BitConverter.GetBytes(strMessage.Length));
            else
                result.AddRange(BitConverter.GetBytes(0));

            //Add the name
            if (strName != null)
                result.AddRange(Encoding.UTF8.GetBytes(strName));

            //And, lastly we add the message text to our array of bytes
            if (strMessage != null)
                result.AddRange(Encoding.UTF8.GetBytes(strMessage));

            return result.ToArray();
        }

        public string strName;      //Name by which the client logs into the room
        public string strMessage;   //Message text
        public Command cmdCommand;  //Command type (login, logout, send message, etcetera)
    }