Write to a python socket server in java

Question

I want to write a string to a socket server in java in bytes, then receive the answer (a known length of bytes).

I have looked around and there are many tutorials, but I can't seem to find a specific function to handle the bytes, also, I don't seem to be able to perform functions on out. This stays red underlined.

import java.io.*;
import java.net.Socket;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;


public class SocketTest {

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


        String hostName = "localhost";
        int portNumber = 10000;

        try (

                //open a socket
                Socket clientSocket = new Socket(hostName, portNumber);


                BufferedReader in =  new BufferedReader( new InputStreamReader(clientSocket.getInputStream()));
                PrintWriter out =  new PrintWriter(clientSocket.getOutputStream(), true);


        ) {

            System.out.print("Something went wrong");

        }

}


    try {

        out.XXX;   //can't seem to execute any function on this. 
    } catch (Exception e) {
        e.printStackTrace();
    }

fge · Accepted Answer · 2014-12-02 19:06:36Z

1

First things first: you are misusing the try-with-resources statement.

The syntax is:

try (
    // declare and open resources here
) {
    // use these resources here
}
// resources are closed here, before you even try to...
catch (SomeException e) {
    // catch exceptions
}

Then, in Java, you have OutputStreams and Writers; the first write bytes, the second write characters; if a Writer wraps an OutputStream, then you need to specify the charset, from which an encoder will be created which will convert your chars into bytes before sending it "along the wire".

In a similar vein, you have InputStreams and Readers, which share the same relationship.

In general, if you do not specify a charset to use for Readers or Writers, the default is used -- and this may, or may not, be UTF-8.

In your code, then:

write the bytes into the first block after try;
specify a Charset to use for your Reader and Writer;
if you use buffering on the write side, don't forget to .flush() after you write (although closing the socket will flush automatically).

The rest is left as an exercise!

edited Dec 2, 2014 at 19:06

answered Dec 2, 2014 at 19:00

fge

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1 Comment

dorien Over a year ago

Thanks so much! The wrong usage of try was confusing the error checker. I'll try the writer assap.

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