Solved - cám ơn mọi người đã đọc qua

mình có làm qua 1 cái chương trình mạng nhiều client kết nỗi tới 1 server dùng fork
nhưng bị lỗi là tuy nhiều cái kết nối đc, nhưng chỉ 1 client hoạt động

code server

#include<stdio.h>
#include<string.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/wait.h>
#inlude<signal.h>
void touppers(char*s) {
    int i;
    for (i=0; i s[i] = toupper(s[i]);
}
void sig_chld(int signo) {
    pid_t pid;
    int stat;
    while ( (pid = waitpid(-1, &stat, WNOHANG)) > 0)
        printf("child %d terminated
", pid);
    return;
}
int main(int argc, char const *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 create");
    // set the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(5500);
    //bind
    if(bind(socket_desc,(struct sockaddr*)&server,sizeof(server))<0) {
        perror("bind failed.Error");
        return 1;
    }
    puts("Bind done!");
    //listen
    listen(socket_desc,3);
    void doit(int client_sock,char *client_message) {
        int read_size;
        while(read_size = recv(client_sock,client_message,2000,0)>0) {
            touppers(client_message);
            write(client_sock,client_message,strlen(client_message));
        }
    }
    //accept connection from client
    puts("Waiting for incoming client");
    c = sizeof(struct sockaddr);
    pid_t pid;
    signal(SIGCHLD,sig_chld);
    // loop
    for( ; ; ) {
        client_sock = accept(socket_desc,(struct sockaddr *)&client,(socklen_t)&c);
        if((pid = fork() ==0)) {
            close(socket_desc);
            doit(client_sock,client_message);
            exit(0);
        }
        close(client_sock);
    }
}

code client

#include<stdio.h>
#include <string.h>   
#include <sys/socket.h>  
#include <arpa/inet.h> 
 
int main(int argc , char *argv[])
{
    int sock,sent_size,sum;
    sum =0;
    char c;
    struct sockaddr_in server;
    char sendbuff[1000] , recvbuff[2000];
     
    //Create socket
    sock = socket(AF_INET , SOCK_STREAM , 0);
    if (sock == -1)
    {
        printf("[Client]: Could not create socket");
    }
    puts("[Client]: Socket created");
     
    server.sin_addr.s_addr = inet_addr("127.0.0.1");
    server.sin_family = AF_INET;
    server.sin_port = htons(5500);
 
    //Connect to remote server
    if (connect(sock , (struct sockaddr *)&server , sizeof(server)) < 0)
    {
        perror("[Client]: Connect failed. Error");
        return 1;
    }
     
    puts("[Client]: Connected
");
     
    //keep communicating with server
    while(1)
    {
        printf("[Client]: Enter message : ");
        fgets(sendbuff,100,stdin);
        if(strlen(sendbuff)==2){
        sendbuff[strlen(sendbuff)-1] = '';
    }
        if((strcmp(sendbuff,"Q")==0)||(strcmp(sendbuff,"q")==0))
            break;
        //Send  data
        if( (sent_size=send(sock , sendbuff , strlen(sendbuff) , 0)) < 0)
        {
            puts("[Client]: Send failed");
            return 1;
        }
        sum = sum +sent_size;
         
        //Receive a reply from the server
        if( recv(sock , recvbuff , 2000 , 0) < 0)
        {
            puts("[Client]: Recv failed");
            break;
        }
         
        puts("Server reply :");
        puts(recvbuff);
        bzero(recvbuff,strlen(recvbuff));
    }
    printf("[Client]: Count sent byte : %d bytes
",sum); 
    close(sock);
    return 0;
}