Question

I tested the performance of transferring data from a program to another over socket on a single computer, and the speed is 120MBytes/s, is it normal?

My server and client programs are both extremely simple.

And my computer is AMD Athlon X2 4000+, 4G DDR2 667 ram, with windows xp sp3.

My friend said it was slow, and should be faster. But I don’t know how can I improve them, or is there any other libraries I can try to get a better speed?

UPDATE

The server and client programs were both on my own computer, a single computer. The network card will limit the speed or not?

---

Server.java

import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class SimpleServer {
    public static void main(String[] args) throws Exception {
        ServerSocket server = new ServerSocket(6666);
        Socket socket = server.accept();
        OutputStream output = socket.getOutputStream();

        byte[] bytes = new byte[10 * 1024]; // 10K
        for (int i = 0; i < bytes.length; i++) { bytes[i] = 12; } // fill the bytes

        // send them again and again
        while (true) {
            output.write(bytes);
        }
    }
}

---

Client.java

public class SimpleClient {

    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("127.0.0.1", 6666);
        InputStream input = socket.getInputStream();
        long total = 0;
        long start = System.currentTimeMillis();

        byte[] bytes = new byte[10240]; // 10K

        // read the data again and again
        while (true) {
            int read = input.read(bytes);
            total += read;
            long cost = System.currentTimeMillis() - start;
            if (cost > 0 && System.currentTimeMillis() % 1000 == 0) {
                 System.out.println("Read " + total + " bytes, speed: " + (total / (1024.0*1024)) / (cost / 1000.0) + " MB/s");
            }
        }
    }

}

Answer 1

Can you give me the output of this program?

public class SimpleServer {
    public static void main(String[] args) throws Exception {
        ServerSocket server = new ServerSocket(6666);
        Socket socket = server.accept();
        OutputStream output = socket.getOutputStream();

        byte[] bytes = new byte[32*1024]; // 32K
        while (true) {
            output.write(bytes);
        }
    }
}
public class SimpleClient {
    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("127.0.0.1", 6666);
        InputStream input = socket.getInputStream();
        long total = 0;
        long start = System.currentTimeMillis();

        byte[] bytes = new byte[32*1024]; // 32K
        for(int i=1;;i++) {
            int read = input.read(bytes);
            if (read < 0) break;
            total += read;
            if (i % 500000 == 0) {
                long cost = System.currentTimeMillis() - start;
                System.out.printf("Read %,d bytes, speed: %,d MB/s%n", total, total/cost/1000);
            }
        }
    }
}

on my machine prints

Read 25,586,204,672 bytes, speed: 5,245 MB/s
Read 53,219,426,304 bytes, speed: 5,317 MB/s
Read 85,018,968,064 bytes, speed: 5,416 MB/s
Read 117,786,968,064 bytes, speed: 5,476 MB/s

---

Try sending 32K blocks many times (for at least 2 seconds) and you should get 400 MB/s or more. e.g. at least 10,000 times.

On a very fast machine you can get 1 GB/s on a single client. With multiple clients you might get 8 GB/s.

Here is an example

Making file transfer more efficient Java

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If you have a 100 Mb card you can expect around 11 MB/s (bytes per second).

Similarly for 1 Gb ethernet youc an expect around 110 MB/s

For a 10 Gig-E ethernet you might get up to 1 GB/s however you might only get half this unles syour system is highly tuned.