Java代理未将任何内容发送回浏览器

Question

I have created a proxy server in Java, (See code below), the thing is, I'm getting response back from the web-server however my client-side of the proxy which handles the connections between clients(browser) and the web-server after a socket has been created with the server side of the proxy. The server side creates a client and sends the request and socket and this is then handled in a new thread. I have a few questions:

First Code is of the Client-side of the proxy second code part is of the Server-side of the proxy

• What type of streams should I use when sending data between browser/proxy/webserver?

• Is it fine to use a String or should I use some type of byte array when sending and receiving from streams?

• Why is the browser not receiving anything from the proxy? Since I can print it out from the console but when writing to the stream nothing happens in the browser.

• Also, why do I need to click "enter" twice in the browser for the proxy to react?

   public class Client implements Runnable { private String request; private String response; private Socket browserSocket; public Client(String request, Socket browserSocket) { this.request = request; this.response = ""; this.browserSocket = browserSocket; } @Override public void run() { /* Send request to web server and get the response. */ this.request = Client.modifyHttpHeader("Connection", "close", this.request); String hostName = Client.getHttpHeader("Host", this.request); if (!hostName.isEmpty()) { try { /* Send request to the web-server. */ Socket socket = new Socket(hostName, 80); OutputStreamWriter osw = new OutputStreamWriter(socket.getOutputStream()); PrintWriter pw = new PrintWriter(osw); pw.write(this.request); pw.flush(); System.out.println("---S:REQUEST---"); System.out.println(this.request); System.out.println("---S:REQUEST---"); /* Receive the response from the web-server. */ BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())); String response = ""; int tmpData; while ((tmpData = br.read()) != -1) { response += (char)tmpData; } this.response = response; socket.close(); /* Close the socket between client-side and web-server. */ /* Send the response back to the browser. */ OutputStreamWriter oswbrowser = new OutputStreamWriter(this.browserSocket.getOutputStream()); PrintWriter pwBrowser = new PrintWriter(oswbrowser); pwBrowser.write(this.response); pwBrowser.flush(); pwBrowser.close(); this.browserSocket.close(); /* Close the socket between client-side and browser. */ System.out.println("---C:RESPONSE---"); System.out.println(this.response); System.out.println("---C:RESPONSE---"); } catch (Exception e) { System.err.println(e.getMessage()); e.printStackTrace(); } } } public String getHttpResponse() { return this.response; } /** * * @param header * The name of the HTTP header. Example: "GET". * Note: Header name is case sensitive. * @param request * The HTTP message. * @return * On success: The value following the HTTP header ": " (colon and whitespace). * On failure: Empty string. */ public static String getHttpHeader(String header, String request) { int startHeaderIndex = request.indexOf(header) + header.length(); int endHeaderIndex = request.indexOf('\\n', startHeaderIndex); /* Could not find the searched header. */ if (startHeaderIndex == -1 || endHeaderIndex == -1) return ""; /* Add 2 to remove ':' and ' '(white space). Decrement 1 to exclude '\\r' and '\\n' */ return request.substring(startHeaderIndex + 2, endHeaderIndex - 1); } /** * * @param header * The name of the HTTP header. Example: "Connection" * Note: The header is case sensitive. * @param value * The new value you want to put. Example: "Close" * @param request * The HTTP message. * @return * On success: A new HTTP request with the modified header value. * On failure: Empty string. * */ public static String modifyHttpHeader(String header, String value, String request) { int startHeaderIndex = request.indexOf(header) + header.length(); int endHeaderIndex = request.indexOf('\\n', startHeaderIndex); /* Could not find the searched header. */ if (startHeaderIndex == -1 || endHeaderIndex == -1) return ""; String newRequest = ""; /* Copy all characters including ':' and ' ' (whitespace) */ for (int i = 0; i < startHeaderIndex + 2; i++) { newRequest += request.charAt(i); } newRequest += value; newRequest += "\\r\\n"; /* Add the rest of the request. */ for (int i = endHeaderIndex + 1; i < request.length(); i++) { newRequest += request.charAt(i); } return newRequest; } } public class Server { public static void main(String[] args) throws Exception{ /* Receiving and parsing port number from command line arguments. */ int ssPort = 0; if (args.length > 1 || args.length == 0){ System.err.println("Only one argument allowed; port number (int)."); System.exit(1); } else { try { ssPort = Integer.parseInt(args[0]); } catch(NumberFormatException exception) { System.err.println("Argument \\"" + args[0] + "\\" must be a number."); System.exit(1); } } ServerSocket serverSocket = new ServerSocket(ssPort); /* Creating the server socket. */ System.out.println("Proxy running on port: " + ssPort); while(true) { System.out.println("Waiting for client..."); Socket clientSocket = serverSocket.accept(); /* Listening for connections. */ BufferedReader bReader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); String request = ""; int tmpData; while ((tmpData = bReader.read()) != -1) { request += (char)tmpData; } Client clientObject = new Client(request, clientSocket); Thread clientThread = new Thread(clientObject); clientThread.start(); /* Start the client thread. */ } } 

  }

Answer 1

Throw it all away. This isn't how proxies are written. An HTTP proxy should:

1. Read one line from the downstream client, to determine whom to connect to upstream, without buffering.
2. Connect upstream.
3. If (2) fails, send an appropriate HTTP response downstream and close the connection.
4. Otherwise, start copying bytes, in both directions, simultaneously.

You should not attempt to assemble the entire request, or even the headers, and the words 'bytes' and 'simultaneously' above are critical. Note that you don't have to do anything about HTTP keep-alive, Connection headers, HTTPS, etc.