Data on udp port

Question

How can we know if any data(response) has arrived on an udp port after sending some request to another PC (for example) as shown below: UdpClient socket = new UdpClient ( 10.99.8.97  5555) ; byte [] data = new byte [] { 0x0b 0xaa 0xbb }; socket.Send(data data.Length); This is required bcoz the response received has to be parsed and the required data has to be displayed in the UI.

Soumya B · Answer

Since i have started to work on class UdpClient i just wanted to know if i could proceed with that only. The problem i am facing is while receiving data on udp port the variable bytesOnSocket is always 0 even when i am sending some data to PC from Hercules.The code is as shown below: Please Note that Hercules is a tool used wherein you can see the communications happening on a udp/tcp port when u bind to that port by giving a port number and IP address UdpClient socket = new UdpClient ( 10.99.8.97  5555); //This is for sending the data and it works fine byte [] data = new byte [] { 0xbb 0x10 0x75 0x12 0x99 0xcc 0xdd }; int datalength = data.Length; socket.Send(data datalength); //This is for receiving the data: byte [] data1 = new byte [1024]; IPAddress ip = IPAddress .Parse( 10.99.8.97 ); IPEndPoint endpoint = new IPEndPoint (ip 5555); int bytesOnSocket = socket.Available; if (bytesOnSocket != 0) { data1 = socket.Receive( ref endpoint); string strData = Encoding .ASCII.GetString(data1); } Please correct me if i am wrong

ramesh p · Answer

try this: This is udp server side program. If u need any thing more reply me.. namespace Server { //The commands for interaction between the server and the client enum Command { Login //Log into the server Logout //Logout of the server Message //Send a text message to all the chat clients List //Get a list of users in the chat room from the server Null //No command } public partial class SGSserverForm : Form { //The ClientInfo structure holds the required information about every //client connected to the server struct ClientInfo { public EndPoint endpoint; //Socket of the client public string strName; //Name by which the user logged into the chat room } //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; byte [] byteData = new byte [1024]; public SGSserverForm() { clientList = new ArrayList (); InitializeComponent(); } private void Form1_Load( object sender EventArgs e) { try { CheckForIllegalCrossThreadCalls = false ; //We are using UDP sockets serverSocket = new Socket ( AddressFamily .InterNetwork SocketType .Dgram ProtocolType .Udp); //Assign the any IP of the machine and listen on port number 1000 IPEndPoint ipEndPoint = new IPEndPoint ( IPAddress .Any 1000); //Bind this address to the server serverSocket.Bind(ipEndPoint); IPEndPoint ipeSender = new IPEndPoint ( IPAddress .Any 0); //The epSender identifies the incoming clients EndPoint epSender = ( EndPoint ) ipeSender; //Start receiving data serverSocket.BeginReceiveFrom (byteData 0 byteData.Length SocketFlags .None ref epSender new AsyncCallback (OnReceive) epSender); } catch ( Exception ex) { MessageBox .Show(ex.Message SGSServerUDP  MessageBoxButtons .OK MessageBoxIcon .Error); } } private void OnReceive( IAsyncResult ar) { try { IPEndPoint ipeSender = new IPEndPoint ( IPAddress .Any 0); EndPoint epSender = ( EndPoint )ipeSender; serverSocket.EndReceiveFrom (ar ref epSender); //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 .Login: //When a user logs in to the server then we add her to our //list of clients ClientInfo clientInfo = new ClientInfo (); clientInfo.endpoint = epSender; 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 joined the room>>> ; 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.endpoint == epSender) { clientList.RemoveAt(nIndex); break ; } ++nIndex; } msgToSend.strMessage =  + msgReceived.strName +  has left the room>>> ; break ; case Command .Message: //Set the text of the message that we will broadcast to all users msgToSend.strMessage = msgReceived.strName + :  + msgReceived.strMessage; break ; case Command .List: //Send the names of all users in the chat room to the new user msgToSend.cmdCommand = Command .List; msgToSend.strName = null ; msgToSend.strMessage = null ; //Collect the names of the user in the chat room foreach ( ClientInfo client in clientList) { //To keep things simple we use asterisk as the marker to separate the user names msgToSend.strMessage += client.strName + * ; } message = msgToSend.ToByte(); //Send the name of the users in the chat room serverSocket.BeginSendTo (message 0 message.Length SocketFlags .None epSender new AsyncCallback (OnSend) epSender); break ; } if (msgToSend.cmdCommand != Command .List) //List messages are not broadcasted { message = msgToSend.ToByte(); foreach ( ClientInfo clientInfo in clientList) { if (clientInfo.endpoint != epSender || msgToSend.cmdCommand != Command .Login) { //Send the message to all users serverSocket.BeginSendTo (message 0 message.Length SocketFlags .None clientInfo.endpoint new AsyncCallback (OnSend) clientInfo.endpoint); } } txtLog.Text += msgToSend.strMessage + 
 ; } //If the user is logging out then we need not listen from her if (msgReceived.cmdCommand != Command .Logout) { //Start listening to the message send by the user serverSocket.BeginReceiveFrom (byteData 0 byteData.Length SocketFlags .None ref epSender new AsyncCallback (OnReceive) epSender); } } catch ( Exception ex) { MessageBox .Show(ex.Message SGSServerUDP  MessageBoxButtons .OK MessageBoxIcon .Error); } } public void OnSend( IAsyncResult ar) { try { serverSocket.EndSend(ar); } catch ( Exception ex) { MessageBox .Show(ex.Message SGSServerUDP  MessageBoxButtons .OK MessageBoxIcon .Error); } } } //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) } }