[网络协议]一个服务端，一个主机，多个从机的tcp通信

本文主要解决的需求是，通过一个服务端控制多个设备。多个设备中分为一主多从。服务端与主机直接通信，主机拆分转发消息到从机，再从从机中接收数据，并整合数据发送给服务端。
不难看出在该需求中，主机既作为tcp的客户端与服务端通信，又作为服务端与多个从机通信。因此涉及到tcp的多线程及同一个端口既作服务端又作客户端。

我用windows系统的通信助手作为服务端。以下为通信助手的界面：

主机和从机的代码在ubuntu虚拟机中执行。虚拟机网络选择桥接模式。下面是我的主机代码：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <strings.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <pthread.h>
//远程服务器端口和IP
#define PORT 1987               //网络助手中的端口号。如果要修改必须一起修改。
#define HOST "192.168.0.83"     //服务端ip，也就是我的windows系统主机ip
//本机服务器端口和IP
#define LOCALPORT 2012               //可自定义，修改的话在从机代码中做对应修改。
#define LOCALHOST "192.168.0.120"    //虚拟机桥接的ip

typedef struct arg {
    int confd;
    struct sockaddr_in client;
} arg_t;

void *threadFun(void *argv)
{
    char recv_buf[1024] = "";
    arg_t *arg = (arg_t*)argv;
    int sockfd = arg->confd;
    struct sockaddr_in client;
    memcpy(&client, &arg->client, sizeof(struct sockaddr_in));
    int buflen = 0;

    while(1)
    {
        buflen = recv(sockfd, recv_buf, sizeof(recv_buf), 0);
        if(buflen > 0) {
            printf("%s:%d recv_buf: %s\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port),recv_buf); // 打印数据
        }
    }  
}


void serve_proc(int port)
{
        printf("server start listening on port %d\n",port);
        int sock_fd;
 
        if ((sock_fd=socket(AF_INET, SOCK_STREAM, 0))==-1){
                printf("socket() error\n");
                return;
        }
 
        struct sockaddr_in server, client;
        bzero(&server,sizeof(server));
        server.sin_family = AF_INET;
        server.sin_port = htons(port);
        server.sin_addr.s_addr = inet_addr(LOCALHOST);
        int reuseport = 1;
 

        setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&reuseport, sizeof(int));
        if (bind(sock_fd, (struct sockaddr *)&server, sizeof(struct sockaddr_in)) < 0){
                perror("bind error");
                return;
        }
        if (listen(sock_fd,5) < 0) {
                perror("listen error");
                return;
        }
 
        char recv_buf[100],send_buf[100];
        int conn_fd;
        int client_size = sizeof(struct sockaddr_in);
        int i = 0;
        while(1){
            conn_fd = accept(sock_fd, (struct sockaddr *)&client, &client_size);
            if (conn_fd > 0){
                pthread_t thread;
                arg_t arg1 = {0};
                arg1.confd = conn_fd;
                memcpy(&arg1.client, &client, sizeof(struct sockaddr_in));
                pthread_create(&thread, NULL, (void*)threadFun, (void*)&arg1);
            }
        }
}

void thread2(void* arg)
{
    int *sock_fd = (int*)arg; 
    char recv_buf[1024] = "";
    int buflen = 0;  
    while(1)
    {
        buflen = recv(*sock_fd, recv_buf, sizeof(recv_buf), 0);
        if(buflen > 0) {
            printf("recv_buf: %s\n",recv_buf);            
        }

    }  
}

int main(int argc, char *argv[])
{
        int sock_fd;
        struct sockaddr_in server,client;
        int flag = 0;
        int reuseport = 1;
        int local_port = LOCALPORT;
 
        if ((sock_fd=socket(AF_INET, SOCK_STREAM, 0))==-1){
                printf("socket() error\n");
                return 1;
        }
        setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&reuseport, sizeof(int));

        bzero(&server,sizeof(server));
        server.sin_family = AF_INET;
        server.sin_port = htons(PORT);
        server.sin_addr.s_addr = inet_addr(HOST);
 

        struct hostent *he;
        he = gethostbyname(LOCALHOST);
        bzero(&client,sizeof(client));
        client.sin_family = AF_INET;
        client.sin_port = htons(local_port);
        client.sin_addr = *((struct in_addr *)he->h_addr_list[0]);;
        setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&reuseport, sizeof(int));
        if (bind(sock_fd, (struct sockaddr *)&client, sizeof(struct sockaddr_in)) < 0){
                perror("bind error");
                return -1;
        }
        if (connect(sock_fd,(struct sockaddr *)&server, sizeof(struct sockaddr)) < 0){
                perror("connect error");
                return 1;
        }
 
        struct sockaddr_in local;
        socklen_t local_len = sizeof(local);

        getsockname(sock_fd, (struct sockaddr *)&local, &local_len);
        char local_ip[100];
        inet_ntop(AF_INET, &local.sin_addr, local_ip, sizeof(local_ip));
        printf("local host %s and port %d\n", local_ip, ntohs(local.sin_port));
        local_port = ntohs(local.sin_port);
        //thread communicate with server
        pthread_t thread;
        pthread_create(&thread, NULL, (void*)thread2, (void*)&sock_fd);
        //thread commmunicate with slave
        serve_proc(LOCALPORT);
}

以下是从机代码：

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

int main()
{
	int sockfd;
	int n;
	struct sockaddr_in servaddr;
	char sendbuf[] = "hello world";

	sockfd = socket(AF_INET,SOCK_STREAM,0);
	bzero(&servaddr,sizeof(servaddr));
    if(sockfd == -1) {
        printf("init failed\n");
    } else {
        printf("init successfully\n");        
    }

	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = inet_addr("192.168.0.120");
	servaddr.sin_port = htons(2012);

	n = connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));
    int buflen = 0;
    if(n == 0){
        while(1)
        {
            buflen = send(sockfd,sendbuf, strlen(sendbuf)+1, 0);
            if(buflen > 0) {
                printf("send successfully\n");                
            }
            sleep(5);
        }
    }
	close(sockfd);

    return 0;
}

下面是运行结果

感觉写的很清楚了。欢迎大佬指点。