Sending Objects over Java Socket really slow

Question

I can't figure out why my Java Server with Socket and ServerSocket is that slow while sending objects. Here a small ping program to demonstrate my problem. If I run both client and server on the same machine, everything is fine ofc (<1ms ping time). However, if I move the Server to a Linux machine I get a ping time of >500ms (ping via command line to that machine says 20ms).

Thanks in advance

Server:

public static void main(String[] args) {
    try {
        ServerSocket serverSocket = new ServerSocket(Integer.parseInt(args[0]));
        Socket socket = serverSocket.accept();

        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());

        oos.writeObject(System.currentTimeMillis());
        long time = (long)ois.readObject();

        System.out.println(System.currentTimeMillis()-time+" ms");

    } catch (Exception e) {
        System.out.println("Some error occured");
        System.exit(1);
    }
}

Client:

public static void main(String[] args) {
    try {
        Socket socket = new Socket(args[0], Integer.parseInt(args[1]));

        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());

        long time = (long)ois.readObject();
        oos.writeObject(time);

    } catch (Exception e) {
        System.out.println("Some error occured");
        System.exit(1);
    }
}

You seem to be comparing server time with client time. It is unlikely that the clocks are synchronized between the two machines to a millisecond. Try rewriting it to measure round trip time, using clock on the same machine: start the clock, send a ping to the server, read response, stop the clock. Also, flush the stream after you write to it. If this does not help, you may want to play around with send and receive buffer sizes, defaults may not be very suitables for messages this small. — Dima
– Dima, Commented Jan 13, 2015 at 14:44
@Dima adjusting the send and receive buffer sizes helped aswell, thanks. Now it is at 30ms same as the ping over command line. — Astraioz
– Astraioz, Commented Jan 14, 2015 at 8:27

GenuinePlaceholder · Accepted Answer · 2017-08-16 23:02:07Z

6

I looked around the web a bit and you are not the only person with this problem. This post also describes the same issue,

Basically, what you should do is instead of:

ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());

You should write:

ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(socket.getOutputStream()));
ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(socket.getInputStream()));

And periodically you would write:

oos.flush();//Write after you send data

edited Aug 16, 2017 at 23:02

answered Jan 13, 2015 at 14:42

GenuinePlaceholder

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Comments

Kright · Accepted Answer · 2016-01-08 14:25:25Z

3

I had the same problem, simple connection had ping about 400ms. Try add this line after socket creating: socket.setTcpNoDelay(true);

answered Jan 8, 2016 at 14:25

Kright

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1 Comment

user3745418 Over a year ago

Many thanks. This reduced a no-reason-whatsoever delay of about 40ms for both client and server running on the same host to less than 1ms.

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