为什么在 Java 中发送 HTTPS 时需要显式 CR？

Question

I'm writing a simple HTTPS client in Java (exploring ideas for interesting/fun labs for my web programming course). In order to get the web server to respond, I have to explicitly add a '\\r' to the end of each line. (If I don't, the web server replies with status 400 and "Your browser sent a request that this server could not understand.")

Should I have to explicitly add "\\r"; or, is there a configuration I'm missing? (In other words, is there a way to tell Java to automatically add the CR?) Interestingly enough, I also tried to run openssl from the command line on my Mac to grab a web page, and I had to add -crlf to the command.

When I use a "regular" socket to connect to and HTTP server on port 80, I don't have this issue (similarly when using telnet ). So, who exactly is being picky? Is the HTTPS protocol different? Is there a way to get Java to use '\\r\\n' instead of just '\\n'?

My code is below:

public class HTTPSClient {
    public static void main(String[] args) throws Exception {

        SSLSocketFactory factory = (SSLSocketFactory) SSLSocketFactory.getDefault();

        SSLSocket socket = (SSLSocket) factory.createSocket("www.emu.edu", 443);

        socket.startHandshake();

        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())));

        out.println("GET / HTTP/1.1\r");
        out.println("host: www.emu.edu\r");
        out.println("connection: close\r");
        out.println("\r");
        out.flush();

        /*
         * Make sure there were no surprises
         */
        if (out.checkError())
            System.out.println("SSLSocketClient:  java.io.PrintWriter error");

        /* read response */
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println(inputLine);
        }

        socket.close();
    }
}

Answer 1

The HTTP standard clearly says that \\r\\n is required. Most servers though accept a simple \\n too - but some actually have a strict (and correct) interpretation of the standard. My guess is that you've tested different servers with "regular" sockets than you did with your Java application. And as with telnet - depending on the setup it might actually send \\r\\n instead of only \\n as line end.