linux上客户端绑定固定端口请求server， 这样可以用客户端的固定端口去请求不同的server

#include <iostream>
#include <sys/select.h>
#include <sys/socket.h>
#include <unistd.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string>
#include <string.h>
#include <event.h>
using namespace std;

#define BUF_SIZE 1024
#define LOCAL_PORT 9092
#define FAULT_SERVER_PORT 9091

/**
 * 客户端绑定固定端口 去 连接到server端
 */
int connectServer(char* ip, int port) {
    int flags = 1;
    int fd = socket(AF_INET, SOCK_STREAM, 0);
    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (void *) &flags, sizeof(flags));
    /* 客户端绑定固定端口*/
    sockaddr_in localAddr;
    bzero(&localAddr, sizeof(localAddr));
    localAddr.sin_family = AF_INET;
    localAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    localAddr.sin_port = htons(LOCAL_PORT);
    bind(fd, (const sockaddr*) &localAddr, sizeof(localAddr));
    if (-1 == fd) {
        cout << "Error, connectServer() quit" << endl;
        return -1;
    }

    struct sockaddr_in remote_addr; //服务器端网络地址结构体
    memset(&remote_addr, 0, sizeof(remote_addr)); //数据初始化--清零
    remote_addr.sin_family = AF_INET; //设置为IP通信
    remote_addr.sin_addr.s_addr = inet_addr(ip); //服务器IP地址
    remote_addr.sin_port = htons(port); //服务器端口号
    int con_result = connect(fd, (struct sockaddr*) &remote_addr,
                             sizeof(struct sockaddr));
    if (con_result < 0) {
        cout << "Connect Error!" << endl;
        close(fd);
        return -1;
    }
    return fd;
}

void on_read(int sock, short event, void* arg) {
    char* buffer = new char[BUF_SIZE];
    memset(buffer, 0, sizeof(char) * BUF_SIZE);
    //--本来应该用while一直循环，但由于用了libevent，只在可以读的时候才触发on_read(),故不必用while了
    int size = read(sock, buffer, BUF_SIZE);
    if (0 == size) { //说明socket关闭
        cout << "read size is 0 for socket:" << sock << endl;
        return;
    }
    cout << "Received from server---" << buffer << endl;
    delete[] buffer;
}

void* init_read_event(void* arg) {
    long long_sock = (long) arg;
    int sock = (int) long_sock;
    //-----初始化libevent，设置回调函数on_read()------------
    struct event_base* base = event_base_new();
    struct event* read_ev = (struct event*) malloc(sizeof(struct event)); //发生读事件后，从socket中取出数据
    event_set(read_ev, sock, EV_READ | EV_PERSIST, on_read, NULL);
    event_base_set(base, read_ev);
    event_add(read_ev, NULL);
    event_base_dispatch(base);
    //--------------
    event_del(read_ev);
    free(read_ev);
    event_base_free(base);
}

/**
* 创建一个新线程，在新线程里初始化libevent读事件的相关设置，并开启event_base_dispatch
*/
void init_read_event_thread(int sock) {
    pthread_t thread;
    pthread_create(&thread, NULL, init_read_event, (void*) sock);
    pthread_detach(thread);
}

int main() {
    cout << "main started" << endl; // prints Hello World!!!
    cout << "Please input server IP:" << endl;
    char ip[16];
    cin >> ip;
    cout << "Please input port:" << endl;
    int port;
    cin >> port;
    cout << "ServerIP is " << ip << " ,port=" << port << endl;
    int socket_fd = connectServer(ip, port);
    cout << "socket_fd=" << socket_fd << endl;
    init_read_event_thread(socket_fd);
    //--------------------------
    char buffer[BUF_SIZE];
    bool isBreak = false;
    while (!isBreak) {
        cout << "Input your data to server(\'q\' or \"quit\" to exit)" << endl;
        cin >> buffer;
        if (strcmp("q", buffer) == 0 || strcmp("quit", buffer) == 0) {
            isBreak = true;
            close(socket_fd);
            break;
        }
        cout << "Your input is " << buffer << endl;
        int write_num = write(socket_fd, buffer, strlen(buffer));
        cout << write_num << " characters written" << endl;
        sleep(1);
    }
    return 0;
}