C中两个服务器的套接字客户端

Question

在我的 C 程序中，我需要与两台服务器通信，一台 IP=X1 PORT=X2，另一台 IP=Y1，PORT=Y2。 IE。我希望能够在我的程序中写入和读取 to/from 两个服务器。例如

write(Server1,buffer1);
read(Server1,buffer1);
write(Server2,buffer2);
read(Server2,buffer2);

我知道如何创建用于与一台服务器通信的单个套接字客户端，但我不确定与两台服务器通信的代码应该是什么样子。有没有人正确指导我 direction/show 我举个例子？

问候西蒙

Answer 1

我很抱歉英语不好，给了一个Windows代码，我暂时不能写Linux，但我希望下次能写。

虽然windows的版本一开始可能有点吓人，但仔细看代码就会明白了。此外，您必须从 Windows 到 POSIX 到 Linux 版本进行一些更改，这是非常直接的（例如，使用 POSIX 线程而不是 windows 线程）。

我已经创建了套接字来接收连接并按照您预期的模式 recv-send 更改消息。每个服务器可能接收的连接数受 MAX_THREADS 限制（每个线程管理一个连接）。请注意，select() returns 具有挂起连接以调用 accept() 的服务器套接字。

#include <winSock2.h>
#include <stdio.h>
#include <stdlib.h>
#include <WS2tcpip.h>
#include <stdint.h>
#include <processthreadsapi.h>
#include <heapapi.h>

#define MAX_THREADS 20
#define MAX_BUFF_SIZE 256

struct thread_list
{
    HANDLE thread;
    struct thread_list *next;
};

struct MyData {
    char name_server[8];
    int sock;
};

void log_error(char *msg)
{
    printf(msg);
    exit(EXIT_FAILURE);
}

void initSocket(int *server, struct sockaddr_in *addr, char *ip, uint16_t porta){

    if ((*server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0){
        log_error("Erro socket\n");
    }

    addr->sin_port = htons(porta);
    addr->sin_addr.s_addr = inet_addr(ip);
    addr->sin_family = AF_INET;

    if((bind(*server, (struct sockaddr *)&addr, sizeof(struct sockaddr_in)) < 0))
        log_error("ERROR bind()");

    if(listen(*server, SOMAXCONN) == SOCKET_ERROR)
        log_error("error listen()");

    return;
}

DWORD WINAPI ThreadFunc(void *data)
{
    char messageFrom[MAX_BUFF_SIZE], messageTo[MAX_BUFF_SIZE];
    struct MyData *ptr = (struct MyData *)data;

    // pattern: recv - send
    while(1)
    {
        recv(ptr->sock, messageFrom, MAX_BUFF_SIZE, 0);

        printf(messageFrom);

        strcpy(messageTo, "Message received. Complete send() message in your way");

        send(ptr->sock, messageTo, strlen(messageTo), 0);
    }

    // Save the whales, feed the hungry, free the mallocs()'s
}


int main( int argc, char **argv) {
    struct sockaddr_in addr1, addr2; 

    int server1, server2;

    struct MyData *pDataArray[MAX_THREADS];
    DWORD   dwThreadIdArray[MAX_THREADS];
    HANDLE  hThreadArray[MAX_THREADS]; 

    // init num current active threads
    int num_threads = 0;

    if(argc < 5)
        log_error("Format: ./prog ip1 port1 ip2 port2\n");

    initSocket(&server1, &addr1, argv[1], (uint16_t)atoi(argv[2]));
    initSocket(&server2, &addr2, argv[3], (uint16_t)atoi(argv[4]));

    int evtsock, novosock;

    fd_set readfds;

    FD_SET(server1, &readfds);
    FD_SET(server2, &readfds);

    struct sockaddr their_addr;
    socklen_t strg_sz = sizeof(their_addr);

    while(1) { //escuta conexoes

        evtsock = select(0, &readfds, NULL, NULL, NULL);
        pDataArray[num_threads]->sock = accept(evtsock, &their_addr, &strg_sz);

        if(pDataArray[num_threads]->sock == INVALID_SOCKET)
            log_error("ERROR accept()");

        if(num_threads == MAX_THREADS){
            // now this program will run forever. It is recommended to manage signals like SIGTERM
            // free mallocated memory and release all resources carefully
            printf("Max connections reached\n");
            continue;
        }

        pDataArray[num_threads] = (struct MyData *) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY,
            sizeof(struct MyData));

        if(evtsock == server1)
            strcpy(pDataArray[num_threads]->name_server, "server1");
        else if(evtsock == server1)
            strcpy(pDataArray[num_threads]->name_server, "server2");
        else
            printf("Unmanaged event\n");

        hThreadArray[num_threads] = CreateThread(NULL, 0, ThreadFunc, &pDataArray[num_threads], 0, NULL);

        num_threads++;
    }

    return 0;
}

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