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();
    }

Answer 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 OutputStream s and Writer s; 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 InputStream s and Reader s, which share the same relationship.

In general, if you do not specify a charset to use for Reader s or Writer s, 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!