Domanda Comunicazione client android server in c linux

Indisparte

Utente Iron
4 Novembre 2020
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Salve a tutti e grazie di star leggendo, sto implementando un semplice progetto universitario lasciato allo sbando più totale. Finito di parlare della bellezza italiana passo al problema.
Devo implementare un'app android che invii e riceva dei messaggi da e verso un server scritto in c che al momento è su una virtual machine ubuntu sul mio pc windows.
Allego il codice:
client.java

Java:
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;

public class MainActivity extends AppCompatActivity {

    private Socket socket;

    private static final int SERVERPORT = 8888;
    private static final String SERVER_IP = "192.168.56.1";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new Thread(new ClientThread()).start();
    }

    public void onClick(View view) {
        try {
            EditText et = findViewById(R.id.EditText01);
            String str = et.getText().toString();
            PrintWriter out = new PrintWriter(new BufferedWriter(
                    new OutputStreamWriter(socket.getOutputStream())),
                    true);
            out.println(str);

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    class ClientThread implements Runnable {
        @Override
        public void run() {

            try {

                InetAddress serverAddr = InetAddress.getByName(SERVER_IP);

                socket = new Socket(serverAddr, SERVERPORT);

            } catch (IOException e1) {
                e1.printStackTrace();
            }

        }

    }
}

server.c
C:
/*
    C socket server example
*/

#include<stdio.h>
#include<string.h>    //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr
#include<unistd.h>    //write

int main(int argc , char *argv[])
{
    int socket_desc , client_sock , c , read_size;
    struct sockaddr_in server , client;
    char client_message[2000];

    //Create socket
    socket_desc = socket(AF_INET , SOCK_STREAM , 0);
    if (socket_desc == -1)
    {
        printf("Could not create socket");
    }
    puts("Socket created");

    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons( 8888 );

    //Bind
    if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
    {
        //print the error message
        perror("bind failed. Error");
        return 1;
    }
    puts("bind done");

    //Listen
    listen(socket_desc , 3);

    //Accept and incoming connection
    puts("Waiting for incoming connections...");
    c = sizeof(struct sockaddr_in);

    //accept connection from an incoming client
    client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c);
    if (client_sock < 0)
    {
        perror("accept failed");
        return 1;
    }
    puts("Connection accepted");

    //Receive a message from client
    while( (read_size = recv(client_sock , client_message , 2000 , 0)) > 0 )
    {
        //Send the message back to client
        write(client_sock , client_message , strlen(client_message));
    }

    if(read_size == 0)
    {
        puts("Client disconnected");
        fflush(stdout);
    }
    else if(read_size == -1)
    {
        perror("recv failed");
    }

    return 0;
}

Controllando il codice socket rimane null e credo sia il motivo principale per cui non avvenga la connessione ma non saprei come rimediare