Write to socket directly and get TCP ZeroWindow

Question

Just as you can see, I send a request to the specific socket every 10 seconds directly( to remain alive and be detected ), but it can only send twice. Using wireshark, I found that the third package I send has TCP ZeroWindow and it cannot send to the server. So does the following packages. Usually, the Window Size should remain at a normal level instead of decreasing all the time. What's wrong with the source code? Any help appreciated!

Three packages I got:

Source code: very simple

public class pediy {

    public static void main(String[] args) throws IOException {

        URL url = new URL("http://bbs.pediy.com");
        Socket socket = null;
        PrintWriter os = null;
        BufferedReader is = null;

        while(true) {

            socket = new Socket(url.getHost(), 80);
            os = new PrintWriter(socket.getOutputStream());

            String request = "GET / HTTP/1.1\nHost: bbs.pediy.com\nProxy-Connection: keep-alive\nAccept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\nUser-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.56 Safari/537.17 CoolNovo/2.0.6.12\nAccept-Encoding: gzip,deflate,sdch\nAccept-Language: en-US;q=0.6,en;q=0.4\nAccept-Charset: utf-8;q=0.7,*;q=0.3\n";
            try {
                while (true) {

                    os.println(request);
                    os.flush();

                    System.out.println("Finished");
                    Thread.sleep(1000*10);
                }

            } catch (Exception e) {
                System.out.println("Error" + e);
            } finally {
                CloseAll(socket, os);
            }
        }
    }

    private static void CloseAll(Socket socket, PrintWriter os) throws IOException {
        if(socket != null) socket.close();
        if(os != null) os.close();
    }
}

Answer 1

这仅表示TCP连接的另一端没有使用（读取）您发送的数据，因此TCP流控制启动以降低发送者的速度。

Answer 2

Well,

1. You aren't sending valid HTTP. The line terminator in HTTP is \\r\\n , not just \\n , and there needs to be a blank line after the headers.

2. You aren't reading the responses.

So the other end will be having some difficulty. You're lucky it hasn't closed the connection already.