< C# Client-Server Socket Program Example | Main | VB .NET Client-Server Socket Program Examples >
Chapter 8 Part 4:
Client (and Server) Sockets Communication
What we have in this chapter 8 Part 4?
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C# Adding Simple Client Socket Project Program Example (Continue)
C# Adding Simple Client Socket Project Program Example (Continue)
Next, let do the client coding. Add the following code to ClientSocket.cs
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// This is a simple TCP and UDP client application. For TCP, the server name is // resolved and a socket is created to attempt a connection to each address // returned until a connection succeeds. Once connected the client sends a "request" // message to the server and shuts down the sending side. The client then loops // to receive the server response until the server closes the connection at which // point the client closes its socket and exits. For UDP, the server name is resolved // and the first address returned is used (since there is no indication that there // is a UDP server at the endpoint). The UDP client then sends a single datagram // "request" message and then waits to receive a response from the server. The client // continues to receive until a zero byte datagram is received. Note that the server // sends several zero byte datagrams but if they are lost, the client will never // exit. // // usage: // Executable_file_name [-c] [-n server] [-p port] [-m message] // [-t tcp|udp] [-x size] // -c If UDP connect the socket before sending // -n server Server name or address to connect/send to // -p port Port number to connect/send to // -m message String message to format in request buffer // -t tcp|udp Indicates to use either the TCP or UDP protocol // -x size Size of send and receive buffers // // sample usage: // The following command line establishes a TCP connection to the given server // on port 5150. The other two command lines are sample server command lines -- // one for IPv4 and one for IPv6. Since the client will attempt to resolve // the server's name, it should attempt to connect over IPv4 and IPv6 as long // as the addresses are registered in DNS. // // Executable_file_name -n server -p 5150 -t tcp // Executable_file_name -l :: -p 5150 -t tcp // Executable_file_name -l 0.0.0.0 -p 5150 -t tcp // // The following command line creates a connected UDP socket that sends // data to the server x.y.z.w on port 5150. While the second entry is the // server command line used. // NOTE: For UDP sockets, the buffer size on the client and server should match // as an exception will be thrown if the receiving buffer is smaller than // the incoming datagram. // // Executable_file_name -n x.y.z.w -p 5150 -t udp -c -x 512 // Executable_file_name -l x.y.z.w -p 5150 -t udp -x 512 // using System; using System.Net; using System.Net.Sockets;
/// <summary> /// This is a simple TCP and UDP based client. /// </summary> namespace SocketClient { class ClientSocket { /// <summary> /// This routine repeatedly copies a string message into a byte array until filled. /// </summary> /// <param name="dataBuffer">Byte buffer to fill with string message</param> /// <param name="message">String message to copy</param> static public void FormatBuffer(byte[] dataBuffer, string message) { byte[ ] byteMessage = System.Text.Encoding.ASCII.GetBytes(message); int index = 0;
// First convert the string to bytes and then copy into send buffer while (index < dataBuffer.Length) { for (int j = 0; j < byteMessage.Length; j++) { dataBuffer[index] = byteMessage[j]; index++; // Make sure we don't go past the send buffer length if (index >= dataBuffer.Length) { break; } } } }
/// <summary> /// Prints simple usage information. /// </summary> static public void usage() { Console.WriteLine("usage: Executable_file_name [-c] [-n server] [-p port] [-m message]"); Console.WriteLine(" [-t tcp|udp] [-x size]"); Console.WriteLine(" -c If UDP connect the socket before sending"); Console.WriteLine(" -n server Server name or address to connect/send to"); Console.WriteLine(" -p port Port number to connect/send to"); Console.WriteLine(" -m message String message to format in request buffer"); Console.WriteLine(" -t tcp|udp Indicates to use either the TCP or UDP protocol"); Console.WriteLine(" -x size Size of send and receive buffers"); Console.WriteLine(" Else, default values will be used..."); }
/// <summary> /// This is the main function for the simple client. It parses the command line and creates /// a socket of the requested type. For TCP, it will resolve the name and attempt to connect /// to each resolved address until a successful connection is made. Once connected a request /// message is sent followed by shutting down the send connection. The client then receives /// data until the server closes its side at which point the client socket is closed. For /// UDP, the socket is created and if indicated connected to the server's address. A single /// request datagram message. The client then waits to receive a response and continues to /// do so until a zero byte datagram is receive which indicates the end of the response. /// </summary> /// <param name="args">Command line arguments</param> static void Main(string[] args) { SocketType sockType = SocketType.Stream; ProtocolType sockProtocol = ProtocolType.Tcp; string remoteName = "localhost", textMessage = "Client: This is a test"; bool udpConnect = false; int remotePort = 5150, bufferSize = 4096;
Console.WriteLine(); usage(); Console.WriteLine();
// Parse the command line for (int i = 0; i < args.Length; i++) { try { if ((args[i][0] == '-') || (args[i][0] == '/')) { switch (Char.ToLower(args[i][1])) { case 'c': // "Connect" the UDP socket to the destination udpConnect = true; break; case 'n': // Destination address to connect to or send to remoteName = args[++i]; break; case 'm': // Text message to put into the send buffer textMessage = args[++i]; break; case 'p': // Port number for the destination remotePort = System.Convert.ToInt32(args[++i]); break; case 't': // Specified TCP or UDP i++; if (String.Compare(args[i], "tcp", true) == 0) { sockType = SocketType.Stream; sockProtocol = ProtocolType.Tcp; } else if (String.Compare(args[i], "udp", true) == 0) { sockType = SocketType.Dgram; sockProtocol = ProtocolType.Udp; } else { usage(); return; } break; case 'x': // Size of the send and receive buffers bufferSize = System.Convert.ToInt32(args[++i]); break; default: usage(); return; } } } catch { usage(); return; } }
Socket clientSocket = null; IPHostEntry resolvedHost = null; IPEndPoint destination = null; byte[ ] sendBuffer = new byte[bufferSize], recvBuffer = new Byte[bufferSize]; int rc;
// Format the string message into the send buffer FormatBuffer(sendBuffer, textMessage);
try { // Try to resolve the remote host name or address resolvedHost = Dns.GetHostEntry(remoteName); Console.WriteLine("Client: GetHostEntry() is OK...");
// Try each address returned foreach (IPAddress addr in resolvedHost.AddressList) { // Create a socket corresponding to the address family of the resolved address clientSocket = new Socket( addr.AddressFamily, sockType, sockProtocol ); Console.WriteLine("Client: Socket() is OK..."); try { // Create the endpoint that describes the destination destination = new IPEndPoint(addr, remotePort); Console.WriteLine("Client: IPEndPoint() is OK. IP Address: {0}, server port: {1}", addr, remotePort);
if ((sockProtocol == ProtocolType.Udp) && (udpConnect == false)) { Console.WriteLine("Client: Destination address is: {0}", destination.ToString()); break; } else { Console.WriteLine("Client: Attempting connection to: {0}", destination.ToString()); } clientSocket.Connect(destination); Console.WriteLine("Client: Connect() is OK..."); break; } catch (SocketException) { // Connect failed, so close the socket and try the next address clientSocket.Close(); Console.WriteLine("Client: Close() is OK..."); clientSocket = null; continue; } }
// Make sure we have a valid socket before trying to use it if ((clientSocket != null) && (destination != null)) { try { // Send the request to the server if ((sockProtocol == ProtocolType.Udp) && (udpConnect == false)) { clientSocket.SendTo(sendBuffer, destination); Console.WriteLine("Client: SendTo() is OK...UDP..."); } else { rc = clientSocket.Send(sendBuffer); Console.WriteLine("Client: send() is OK...TCP..."); Console.WriteLine("Client: Sent request of {0} bytes", rc);
// For TCP, shutdown sending on our side since the client won't send any more data if (sockProtocol == ProtocolType.Tcp) { clientSocket.Shutdown(SocketShutdown.Send); Console.WriteLine("Client: Shutdown() is OK..."); } }
// Receive data in a loop until the server closes the connection. For // TCP this occurs when the server performs a shutdown or closes // the socket. For UDP, we'll know to exit when the remote host // sends a zero byte datagram. while (true) { if ((sockProtocol == ProtocolType.Tcp) || (udpConnect == true)) { rc = clientSocket.Receive(recvBuffer);
Console.WriteLine("Client: Receive() is OK..."); Console.WriteLine("Client: Read {0} bytes", rc); } else { IPEndPoint fromEndPoint = new IPEndPoint(destination.Address, 0); Console.WriteLine("Client: IPEndPoint() is OK..."); EndPoint castFromEndPoint = (EndPoint)fromEndPoint; rc = clientSocket.ReceiveFrom(recvBuffer, ref castFromEndPoint); Console.WriteLine("Client: ReceiveFrom() is OK..."); fromEndPoint = (IPEndPoint)castFromEndPoint; Console.WriteLine("Client: Read {0} bytes from {1}", rc, fromEndPoint.ToString()); }
// Exit loop if server indicates shutdown if (rc == 0) { clientSocket.Close(); Console.WriteLine("Client: Close() is OK..."); break; } } } catch (SocketException err) { Console.WriteLine("Client: Error occurred while sending or receiving data."); Console.WriteLine(" Error: {0}", err.Message); } } else { Console.WriteLine("Client: Unable to establish connection to server!"); } } catch (SocketException err) { Console.WriteLine("Client: Socket error occurred: {0}", err.Message); } } } } |
Build the client program and make sure there is no error.
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Run the client program.
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Well, we can’t see the real communication without running both client and server programs simultaneously. In this case we copy both executables (under the Debug folder – SimpleSocketCS.exe - server and SocketClient.exe - client) to the C:\, run the server program and then the client program at the command prompt.
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If the following Windows Security Alert box displayed, click the Unblock button.
Run the server program and the following is a sample output.
Next, run the client program.
The following is the server output screenshot when the communication was completed.
