/** C# Programming Tips & Techniques by Charles Wright, Kris Jamsa Publisher: Osborne/McGraw-Hill (December 28, 2001) ISBN: 0072193794 */ // Proxy.cs -- Implements a multi-threaded Web proxy server // // Compile this program with the following command line: // C:>csc Proxy.cs using System; using System.Net; using System.Net.Sockets; using System.Text; using System.IO; using System.Threading; namespace nsProxyServer { public class ProxyServer { static public void Main (string [] args) { int Port = 3125; if (args.Length > 0) { try { Port = Convert.ToInt32 (args[0]); } catch { Console.WriteLine ("Please enter a port number."); return; } } try { // Create a listener for the proxy port TcpListener sockServer = new TcpListener (Port); sockServer.Start (); while (true) { // Accept connections on the proxy port. Socket socket = sockServer.AcceptSocket (); // When AcceptSocket returns, it means there is a connection. Create // an instance of the proxy server class and start a thread running. clsProxyConnection proxy = new clsProxyConnection (socket); Thread thrd = new Thread (new ThreadStart (proxy.Run)); thrd.Start (); // While the thread is running, the main program thread will loop around // and listen for the next connection request. } } catch (IOException e) { Console.WriteLine (e.Message); } } } class clsProxyConnection { public clsProxyConnection (Socket sockClient) { m_sockClient = sockClient; } Socket m_sockClient; //, m_sockServer; Byte [] readBuf = new Byte [1024]; Byte [] buffer = null; Encoding ASCII = Encoding.ASCII; public void Run () { string strFromClient = ""; try { // Read the incoming text on the socket/ int bytes = ReadMessage (m_sockClient, readBuf, ref strFromClient); // If it's empty, it's an error, so just return. // This will termiate the thread. if (bytes == 0) return; // Get the URL for the connection. The client browser sends a GET command // followed by a space, then the URL, then and identifer for the HTTP version. // Extract the URL as the string betweeen the spaces. int index1 = strFromClient.IndexOf (' '); int index2 = strFromClient.IndexOf (' ', index1 + 1); string strClientConnection = strFromClient.Substring (index1 + 1, index2 - index1); if ((index1 < 0) || (index2 < 0)) { throw (new IOException ()); } // Write a messsage that we are connecting. Console.WriteLine ("Connecting to Site " + strClientConnection); Console.WriteLine ("Connection from " + m_sockClient.RemoteEndPoint); // Create a WebRequest object. WebRequest req = (WebRequest) WebRequest.Create (strClientConnection); // Get the response from the Web site. WebResponse response = req.GetResponse (); int BytesRead = 0; Byte [] Buffer = new Byte[32]; int BytesSent = 0; // Create a response stream object. Stream ResponseStream = response.GetResponseStream(); // Read the response into a buffer. BytesRead = ResponseStream.Read(Buffer,0,32); StringBuilder strResponse = new StringBuilder(""); while (BytesRead != 0) { // Pass the response back to the client strResponse.Append(Encoding.ASCII.GetString(Buffer, 0, BytesRead)); m_sockClient.Send(Buffer, BytesRead, 0); BytesSent += BytesRead; // Read the next part of the response BytesRead = ResponseStream.Read(Buffer, 0, 32); } } catch (FileNotFoundException e) { SendErrorPage (404, "File Not Found", e.Message); } catch (IOException e) { SendErrorPage (503, "Service not available", e.Message); } catch (Exception e) { SendErrorPage (404, "File Not Found", e.Message); Console.WriteLine (e.StackTrace); Console.WriteLine (e.Message); } finally { // Disconnect and close the socket. if (m_sockClient != null) { if (m_sockClient.Connected) { m_sockClient.Close (); } } } // Returning from this method will terminate the thread. } // Write an error response to the client. void SendErrorPage (int status, string strReason, string strText) { SendMessage (m_sockClient, "HTTP/1.0" + " " + status + " " + strReason + "\\r\\n"); SendMessage (m_sockClient, "Content-Type: text/plain" + "\\r\\n"); SendMessage (m_sockClient, "Proxy-Connection: close" + "\\r\\n"); SendMessage (m_sockClient, "\\r\\n"); SendMessage (m_sockClient, status + " " + strReason); SendMessage (m_sockClient, strText); } // Send a string to a socket. void SendMessage (Socket sock, string strMessage) { buffer = new Byte [strMessage.Length + 1]; int len = ASCII.GetBytes (strMessage.ToCharArray(), 0, strMessage.Length, buffer, 0); sock.Send (buffer, len, 0); } // Read a string from a socket. int ReadMessage (Socket sock, byte [] buf, ref string strMessage) { int iBytes = sock.Receive (buf, 1024, 0); strMessage = Encoding.ASCII.GetString (buf); return (iBytes); } } }
