Ping Utility freezing up...?

[Raenius]

Hi all,

I am working on incorporating the C# ping Utility from

http://www.csharphelp.com/archives/archive6.html

into my own winform program.

I had to adjust some things (variables etc) for it to work but never mind that. I am currently calling the function with IP addresses I get out of my Database, this all goes well with no problems.

When I call the function and the host is up I get the ping back and the reply time perfectly BUT when the host is down, the program freezes and stops working until I force it to close...

Here is the code:

public void PingHost(string host) // was STATIC
		{
			//Declare the IPHostEntry 
	        IPHostEntry serverHE=null, fromHE;
	        int nBytes = 0;
	        int dwStart = 0, dwStop = 0;
			//Initilize a Socket of the Type ICMP
			Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);

	        // Get the server endpoint
			try
			{
				serverHE = Dns.GetHostByName(host);
			}
			catch(Exception m)
			{
				MessageBox.Show("Host not found");
				MessageBox.Show(m.ToString(),"Error Message");
				return;
			}

			try
			{
			// Convert the server IP_EndPoint to an EndPoint
            IPEndPoint ipepServer = new IPEndPoint(serverHE.AddressList[0], 0);
			EndPoint epServer = (ipepServer);

			// Set the receiving endpoint to the client machine
			fromHE = Dns.GetHostByName(Dns.GetHostName());
	        IPEndPoint ipEndPointFrom = new IPEndPoint(fromHE.AddressList[0], 0);        
	        EndPoint EndPointFrom = (ipEndPointFrom);

	        int PacketSize = 0;
			IcmpPacket packet = new IcmpPacket();
	        // Construct the packet to send
	        packet.Type = ICMP_ECHO; //8
	        packet.SubCode = 0;
	        packet.CheckSum = UInt16.Parse("0");
	        packet.Identifier   = UInt16.Parse("45"); 
	        packet.SequenceNumber  = UInt16.Parse("0"); 
			int PingData = 32; // sizeof(IcmpPacket) - 8;
	        packet.Data = new Byte[PingData];
			//Initilize the Packet.Data
	        for (int i = 0; i < PingData; i++)
			{
				packet.Data[i] = (byte)'#';
			}
	             
			//Variable to hold the total Packet size
	        PacketSize = PingData + 8;
	        Byte [] icmp_pkt_buffer = new Byte[ PacketSize ]; 
	        Int32 Index = 0;
			//Call a Methos Serialize which counts
			//The total number of Bytes in the Packet
	        Index = Serialize(  
	                      packet, 
	                      icmp_pkt_buffer, 
	                      PacketSize, 
	                      PingData );
			//Error in Packet Size
	        if( Index == -1 )
			{
				MessageBox.Show("Error in Making Packet");
				return ;
			}
          
	            // now get this critter into a UInt16 array
	         
	            //Get the Half size of the Packet
	            Double double_length = Convert.ToDouble(Index);
				Double dtemp = Math.Ceiling( double_length / 2);  
				int cksum_buffer_length = Convert.ToInt32(dtemp);
				//Create a Byte Array
	            UInt16 [] cksum_buffer = new UInt16[cksum_buffer_length];
				//Code to initilize the Uint16 array 
	            int icmp_header_buffer_index = 0;
	            for( int i = 0; i < cksum_buffer_length; i++ ) {
					cksum_buffer[i] = 
	                   BitConverter.ToUInt16(icmp_pkt_buffer,icmp_header_buffer_index);
	                icmp_header_buffer_index += 2;
	            }
				//Call a method which will return a checksum             
	            UInt16 u_cksum = checksum(cksum_buffer, cksum_buffer_length);
				//Save the checksum to the Packet
	            packet.CheckSum  = u_cksum; 
	            
	            // Now that we have the checksum, serialize the packet again
	            Byte [] sendbuf = new Byte[ PacketSize ]; 
	            //again check the packet size
	            Index = Serialize(  
	                        packet, 
	                        sendbuf, 
	                        PacketSize, 
	                        PingData );
				//if there is a error report it
	            if( Index == -1 )
				{
					MessageBox.Show("Error in Making Packet");
					return ;
				}
	                

	            dwStart = System.Environment.TickCount; // Start timing
				//send the Pack over the socket
	            if ((nBytes = socket.SendTo(sendbuf, PacketSize, 0, epServer)) == SOCKET_ERROR) 
				{		
	                MessageBox.Show("Socket Error cannot Send Packet");
	            }
				// Initialize the buffers. The receive buffer is the size of the
	            // ICMP header plus the IP header (20 bytes)
	            Byte [] ReceiveBuffer = new Byte[256]; 
	            nBytes = 0;
				//Receive the bytes
	            bool recd =false ;
				int timeout=0 ;
 
				//loop for checking the time of the server responding 
				while(!recd)
				{
					nBytes = socket.ReceiveFrom(ReceiveBuffer, 256, 0, ref EndPointFrom);
					if (nBytes == SOCKET_ERROR) 
					{
						MessageBox.Show("Host not Responding") ;
						recd=true ;
						break;
					}
					else if(nBytes>0)
					{
						dwStop = System.Environment.TickCount - dwStart; // stop timing
						MessageBox.Show("Reply from "+epServer.ToString()+" in "+dwStop+"MS :Bytes Received"+nBytes);
						recd=true;
						break;
					}
					timeout=System.Environment.TickCount - dwStart;
					if(timeout>1000)
					{
						MessageBox.Show("Time Out") ;
						recd=true;
					}
					
				}
	            
			//close the socket
			socket.Close();
			}
			catch(Exception n)
			{
			MessageBox.Show(n.ToString());
			}
		}

Does anyone have an idea what is going on? I thought it was the:

 IPEndPoint ipepServer = new IPEndPoint(serverHE.AddressList[0], 0);

part which can't be done if the host is down, I put in into a big try/catch situation but no errors are reported the entire program just freezes.

I hope someone can help me.

Kind regards,

Raenius





"Free will...is an illusion"

 

[Raenius]

I think I have localised the error to indeed the:

serverHE = Dns.GetHostByName(host);

and after that the:

IPEndPoint ipepServer = new IPEndPoint(serverHE.AddressList[0], 0);
EndPoint epServer = (ipepServer);

Weird thing is that it does not give any exceptions! :'(

I hope that someone can help me...

- Raenius 



"Free will...is an illusion"