C中的多线程服务器/客户端实现 [英] multithread server/client implementation in C

问题描述

我刚刚开始学习基本的网络概念.我正在尝试在 C 中实现一个多线程服务器-客户端程序.但问题是不是为客户端运行多个窗口/终端/实例，我应该使用 fork() 来创建客户端的子级.因此，通过创建客户端的子级，将创建多个客户端.现在这些子客户端中的每一个都将在一个线程上与服务器通信.

I have just started learning basic networking concepts.I am trying to implement a multithread server-client prog in C.but the problem is instead of running multiple windows/terminals/instances for clients,i should use fork() to create children of client.so by creating children of client multiple clients will be created.now each of these child clients will communicate with the server on a thread.

之前我创建了一个类似的程序，但对于多个客户端，您必须为客户端打开多个窗口并运行所有这些窗口.

Earlier i created a similar prog but in that for multiple client you have to open multiple windows for clients and run all of them.

我在修改我的代码时遇到了麻烦(在服务器和客户端代码中.我认为服务器一没问题.但我不知道在客户端程序中 fork() 的位置以及应该进行哪些更改).

I am having trouble where to modify my code (both in server and client ones.I think server one is ok.but i am having no idea where to fork() in client program and what changes should be made).

实际上我不想打开多个窗口来运行多个客户端，这就是我使用 fork() 创建它的多个副本的原因.有没有其他方法可以创建多个客户端并将它们连接到我的服务器程序通过线程.

Actually i don't want to open multiple windows to run multiple client,thats why i am using fork() to create multiple copies of it.Is there any other way by which i can create multiple clients and connect them to my server prog via threads.

服务器:

// socket server example, handles multiple clients using threads

#include<stdio.h>
#include<string.h>    //strlen
#include<stdlib.h>    //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr
#include<unistd.h>    //write
#include<pthread.h> //for threading , link with lpthread

//the thread function
void *connection_handler(void *);

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

    //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( 3000 );

    //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);

        c=sizeof(struct sockaddr_in);
       while(client_sock=accept(socket_desc,(struct sockaddr*)&client,(socklen_t*)&c))
       {
        puts("Connection accepted");

        pthread_t sniffer_thread;
        new_sock = malloc(1);
        *new_sock = client_sock;

        if( pthread_create( &sniffer_thread , NULL ,  connection_handler , (void*) new_sock) < 0)
        {
            perror("could not create thread");
            return 1;
        }

        puts("Handler assigned");
    }

    if (client_sock < 0)
    {
        perror("accept failed");
        return 1;
    }
    return 0;
}
/*
  This will handle connection for each client
  */
void *connection_handler(void *socket_desc)
{
    //Get the socket descriptor
    int sock = *(int*)socket_desc;
    int n;

        char    sendBuff[100], client_message[2000];

      while((n=recv(sock,client_message,2000,0))>0)
      {

        send(sock,client_message,n,0);
      }
      close(sock);

      if(n==0)
      {
        puts("Client Disconnected");
      }
      else
      {
        perror("recv failed");
      }
    return 0;
}

客户:

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

#define MAX_SIZE 50

int main()
{
    int sock_desc;
    struct sockaddr_in serv_addr;
    char sbuff[MAX_SIZE],rbuff[MAX_SIZE];

    if((sock_desc = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        printf("Failed creating socket
");

    bzero((char *) &serv_addr, sizeof (serv_addr));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serv_addr.sin_port = htons(3000);

    if (connect(sock_desc, (struct sockaddr *) &serv_addr, sizeof (serv_addr)) < 0) {
        printf("Failed to connect to server
");
        return -1;
    }

    printf("Connected successfully - Please enter string
");
    while(fgets(sbuff, MAX_SIZE , stdin)!=NULL)
    {
      send(sock_desc,sbuff,strlen(sbuff),0);

          if(recv(sock_desc,rbuff,MAX_SIZE,0)==0)
           printf("Error");
          else
           fputs(rbuff,stdout);

       bzero(rbuff,MAX_SIZE);//to clean buffer-->IMP otherwise previous word characters also came
    }
        close(sock_desc);
    return 0;

}

推荐答案

您可以使用线程创建多个客户端.为每个客户端创建一个单独的线程，然后从线程处理程序连接到服务器.我不确定这是不是一个好方法.

You can create multiple clients using thread. Create a separate thread for each client and then from thread handler connect to the server. I am not sure if it is a good way or not.

代码:

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

#define MAX_SIZE 50
#define NUM_CLIENT 5
void *connection_handler(void *socket_desc);
int main()
{
    int socket_desc , new_socket , c , *new_sock, i;
    pthread_t sniffer_thread;
    for (i=1; i<=NUM_CLIENT; i++) {
        if( pthread_create( &sniffer_thread , NULL ,  connection_handler , (void*) i) < 0)
        {
            perror("could not create thread");
            return 1;
        }
        sleep(3);
    }
    pthread_exit(NULL);
    return 0;
}

void *connection_handler(void *threadid)
{
    int threadnum = (int)threadid;
    int sock_desc;
    struct sockaddr_in serv_addr;
    char sbuff[MAX_SIZE],rbuff[MAX_SIZE];

    if((sock_desc = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        printf("Failed creating socket
");

    bzero((char *) &serv_addr, sizeof (serv_addr));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serv_addr.sin_port = htons(8888);

    if (connect(sock_desc, (struct sockaddr *) &serv_addr, sizeof (serv_addr)) < 0) {
        printf("Failed to connect to server
");
    }

    printf("Connected successfully client:%d
", threadnum);
    while(1)
    {
        printf("For thread : %d
", threadnum);
        fgets(sbuff, MAX_SIZE , stdin);
        send(sock_desc,sbuff,strlen(sbuff),0);

        if(recv(sock_desc,rbuff,MAX_SIZE,0)==0)
            printf("Error");
        else
           fputs(rbuff,stdout);

        bzero(rbuff,MAX_SIZE);
        sleep(2);
    }
    close(sock_desc);
    return 0;
}

为了理解目的，我使用了 sleep.

For understanding purpose, i used sleep.

参考:

http://www.amazon.com/UNIX-Network-Programming-Richard-Stevens/dp/0139498761

http://beej.us/guide/bgnet/

https://computing.llnl.gov/tutorials/pthreads/

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