Java BufferedReader，如果不阻塞怎么调用？

Question

I have 2 sockets and I am using BufferedReader around it's InputStreams. What I am trying to do is take all input from the first socket and send it to the other socket (and visa versa).

The problem is that if the first one does not send a message, it will still block on the first readLine() even though the 2nd socket has already sent some data and is ready. I would like to continue with this simple approach of using no additional threads.

Here's some code that I wrote up, as you can see I have 2 BufferedReaders (in0 and in1) , the program gets stuck at in0.readLine() (blocking).

private void network()
{
    PrintWriter out0 = null, out1 = null;
    BufferedReader in0 = null,in1 = null;
    try{
            //clients[] is an array of Socket[2]
        in0 = new BufferedReader(new InputStreamReader(clients[0].getInputStream()));
        out0 = new PrintWriter(clients[0].getOutputStream(), true);
        in1 = new BufferedReader(new InputStreamReader(clients[1].getInputStream()));
        out1 = new PrintWriter(clients[1].getOutputStream(), true);
      } catch (IOException e) {
        System.out.println("Accept failed: 4445");
        System.exit(-1);
      }

    int count = 1;
    while(true)
    {
        System.out.println("network check loop # " + count);
        ++count;
        String nextMessage = null;
        try {
            if( (nextMessage = in0.readLine()) != null)
            {
                this.relayMessage(nextMessage,out1);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        System.out.println("Middle of network check loop");
        nextMessage = null;

        try {
            if((nextMessage = in1.readLine()) != null)
            {
                this.relayMessage(nextMessage,out0);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

How can I just skip that statement if in0 is not ready to give me some data? I have seen BufferedReader's ready() method and have attempted to use in0.ready() && readLine() but this causes an infinite loop as neither of the bufferedreaders appear to ever be 'ready'. As well, I am certain that the messages being sent over the socket end in newline characters so readLine() should process correctly!

Any ideas?

Answer 1

在这里， break and Continue关键字是您的朋友。

Answer 2

尝试使用setSoTimeout在您的read（）上放置一个超时，然后如果计时器已过期， 则只需要捕获SocketTimeoutException。

Answer 3

The simplest approach is to use two threads. This way you don't have to write your own scheduling code to determine which thread should be running. BTW: The code to copy from one socket to another is the same in each thread, reducing duplication.

To manage your threads I would use an ExecutorService which will make shutting downt eh threads easier.