套接字连接C ++和Java

Question

我用C ++编写服务器，用java编写客户端，通过套接字进行通信但是当我在C ++服务器中使用函数write时，服务器和客户端之间的连接关闭，客户端读取null 这是代码：

C ++中的服务器

#include<stdio.h>
#include<stdlib.h>
#include<sstream>
#include<string>
#include<netdb.h>
#include<netinet/in.h>
#include<string.h>
#include<iostream>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>

using namespace std;

void doprocessing (int sock, int cliente);
void sendM(int socket,int client);

int main(int argc, char *argv[]) {
   int sockfd, newsockfd, portno,cliente;
   char buffer[256];
   struct sockaddr_in serv_addr, cli_addr;
   int n, pid;
   socklen_t clilen;


   sockfd = socket(AF_INET, SOCK_STREAM, 0);

   if (sockfd < 0) {
      perror("ERROR opening socket");
      exit(1);
   }

   /* Initialize socket structure */
   bzero((char *) &serv_addr, sizeof(serv_addr));
   portno = 8080;

   serv_addr.sin_family = AF_INET;
   serv_addr.sin_addr.s_addr = INADDR_ANY;
   serv_addr.sin_port = htons(portno);

   /* Now bind the host address using bind() call.*/
   if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
      perror("ERROR on binding");
      exit(1);
   }

   /* Now start listening for the clients, here
      * process will go in sleep mode and will wait
      * for the incoming connection
   */

   listen(sockfd,5);
   clilen = sizeof(cli_addr);
   cout<<"Servidor Iniciado..."<<endl;

   while (1) {
      newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
      cliente=cliente+1;

      if (newsockfd < 0) {
         perror("ERROR aceptando conexion");
         exit(1);
      }

      /* Create child process */
      pid = fork();

      if (pid < 0) {
         perror("ERROR on fork");
         exit(1);
      }

      if (pid == 0) {

         cout<<"Nueva conexion "<<cliente<<endl;
         close(sockfd);
         doprocessing(newsockfd,cliente);
         exit(0);
      }
      else {
         close(newsockfd);
      }

   }
}

void doprocessing (int sock, int cliente1) {
   int n;
   char buffer[256], *msj;
   bzero(buffer,256);
   n = read(sock,buffer,255);
   if (n < 0) {
      perror("ERROR leyendo de socket");
      exit(1);
   }
   cout<<"Mensaje de cliente "<<cliente1<<":"<<buffer<<endl;
   sendM(sock,cliente1);

}

void sendM(int socket, int client){
    char *buff;
    int n;
    cout << "\nServidor: ";
    cin >> buff;
    n=write(socket, buff,strlen(buff));
    doprocessing(socket,client);
    cout<<n<<endl;
    if(n<0){
        cout<<"Error enviando respuesta"<<endl;
    }
    cout<<n<<endl;

}

这是客户端代码

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

public class Conexion {

    BufferedReader lector = null;
    PrintWriter escritor = null;
    public Socket sockete;
    Thread principal=null;
    String mensaje_in=null;

    public Conexion(){
        Conectar();
    }
    public void Conectar(){
        principal = new Thread(new Runnable() {
            public void run() {
                try {
                        if(sockete==null){
                        sockete = new Socket("192.168.0.103", 8080);
                        Leer();}

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

    }
    public void Leer(){
        Thread leer_hilo=new Thread(new Runnable(){
            public void run(){

                try{
                    lector=new BufferedReader(new InputStreamReader(sockete.getInputStream()));
                    while(true){
                        String mensaje= lector.readLine();
                        if (lector==null){
                            System.out.println("NO se conecta");
                        }else{
                             System.out.println("Este es el mensaje: "+mensaje);
                        }
                    }

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

                  }
            }

        });
        leer_hilo.start();

    }

    /**
     * Envia datos al servidor
     * @param dato
     */
    public void Escribir(String dato){

        try{
            escritor= new PrintWriter(sockete.getOutputStream(), true);
            escritor.println(dato);
            System.out.println(dato);
        }catch(Exception ex){
            ex.printStackTrace();
        }

    }
 }