无法从套接字的 setSoTimeout 获取 SocketTimeoutException

Question

I'm trying to implement a basic webserver with HTTP 1.1 functionality. The server has a timeout of 2 seconds - if no new packets are requested for 2 seconds, the socket is closed.

private void start(int port) throws IOException{
  System.out.println("Starting server on port " + port);
  ServerSocket serverSocket = new ServerSocket(port);
  try{
    while(true){
      Socket clientSocket = serverSocket.accept();
      handleClientSocket(clientSocket, serverSocket);
    }
  }catch(SocketTimeoutException e){
    System.out.println("Time's up");
  }
}

/**
 * Handles requests sent by a client
 * @param  client Socket that handles the client connection
 */
private void handleClientSocket(Socket client, ServerSocket server) throws IOException, SocketTimeoutException {

  BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
  String line;

  while((line = in.readLine()) != null && !line.isEmpty()){
    String[] header = line.split(" ");
    if(header[0].equals("GET")){
      switch(header[2]){
        case "HTTP/1.0":
          generate(client, in.readLine(), header);
          System.out.println("close");
          client.close();
        break;
        case "HTTP/1.1":
          generate(client, in.readLine(), header);
          client.setSoTimeout(2000); 
        break;
        default:
          System.out.println("This is not suppose to happen.");
        break;
      }
    }
  }
}

The program reads a buffered input of packets in the following format:

GET \background.png HTML\1.1
Host: localhost:8000

This input is repeatedly read till the buffered input is empty. Because the setSoTimeout is nested in the while loop, every new packet processed will reset the timer to 2000ms.

The method encapsulating this, handleClientSocket , throws a SocketTimeoutException , which is caught by the try-catch block from the start method.

Hence, when the timeout is reached it should print Time's up .

I am able to connect to the webserver and get a working page, however, I am not able to simulate the "connection closed" ~ 2 seconds after the request is sent.

Answer 1

 while(!(line = in.readLine()).isEmpty()){

Invalid. You must test it for null first:

 while((line = in.readLine()) != null && !line.isEmpty()){

The program reads a buffered input of packets in the following format:

GET \background.png HTML\1.1

No it doesn't. It looks for HTTP/1.1 , and the backslashes should be forward slashes in HTTP, so it should be:

GET /background.png HTTP/1.1

That's what you're testing for.

And note that the line separator in HTTP is defined as \\r\\n , not just \\n .

This input is repeatedly read till the buffered input is empty.

No it isn't. It is read until a blank line is read, the peer closes the connection, or a read timeout occurs. readLine() does not return null, or an empty line, when 'the buffered input is empty'. It blocks.

Because the setSoTimeout is nested in the while loop, every new packet processed will reset the timer to 2000ms.

Unnecessary. Once set, the timeout stays set. You don't need to set it every time around the loop. You should set it before the loop. At present there is no read timeout at all on the first read.

You are also discarding every odd-numbered line. This doesn't seem right.

If you aren't getting SocketTimeoutExceptions from this code, data is arriving within the timeout period every time you call readLine() .

Or else you are blocking in the first readLine() , when there is no read timeout yet.

Or else you are getting NullPointerExceptions because of the first error.

EDIT Or else you aren't in readLine() at all. You aren't. You have handled one entire request, read it to the end of the headers, and then returned to the main method. So, no read timeout. I managed to get a SocketTimeoutException by restructuring your accept loop as follows:

    while (true)
    {
        try (Socket clientSocket = serverSocket.accept())
        {
            System.out.println("accepted " + clientSocket);
            for (;;)
            {
                handleClientSocket(clientSocket, serverSocket);
            }
        }
        catch (SocketTimeoutException e)
        {
            System.out.println("Time's up");
        }
        System.out.println("request handling ended");
    }