同时处理TCP、UDP的服务

我们讨论的服务器程序都只能监听一个端口。在实际应用中，有不少服务器程序能同时监听多个端口。
从bind系统调用来看，一个socket只能和一个socket地址绑定，即一个socket只能用来监听一个端口。因此服务器如果要同时监听多个端口，就必须创建多个socket，并将它们分别绑定到各个端口上。这样就可以使用IO复用技术。
另外，即使是同一个端口，如果服务器要同时处理该端口上的TCP、UDP请求，也需要创建两个不同的socket：一个是流socket，一个是数据报socket，并将它们都绑定在该端口上。

#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <pthread.h>
#include <libgen.h>

#define MAX_EVENT_NUMBER    1024
#define TCP_BUFFER_SIZE     512
#define UDP_BUFFER_SIZE     1024
#define BACKLOG             5

int setnonbolcking (int fd) {
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

void addfd(int epollfd, int fd) {
    epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN | EPOLLET;
    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
    setnonbolcking(fd);
}

int main(int argc, char* argv[]) {
    if (argc <= 2) {
        printf("usage: %s ip_address port_number\n", basename(argv[0]));
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi(argv[2]);

    struct sockaddr_in address;
    bzero(&address, sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port = htons(port);

    // 创建TCP socket，并将其绑定到端口port上
    int listenfd = socket(PF_INET, SOCK_STREAM, 0);
    assert(listenfd >= 0);

    int ret = bind(listenfd, (struct sockaddr*)&address, sizeof(address));
    assert(ret != -1);

    ret = listen(listenfd, BACKLOG);
    assert(ret != -1);

    // 创建UDP socket，并将其绑定到端口port上
    bzero(&address, sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port = htons(port);

    int udpfd = socket(PF_INET, SOCK_DGRAM, 0);
    assert(udpfd >= 0);

    ret = bind(udpfd, (struct sockaddr*)&address, sizeof(address));
    assert(ret != -1);

    epoll_event events[MAX_EVENT_NUMBER];
    int epollfd = epoll_create(1);
    assert(epollfd != -1);

    // 注册TCP socket和UDP socket上的可读事件
    addfd(epollfd, listenfd);
    addfd(epollfd, udpfd);

    while (1) {
        int number = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
        if (number < 0) {
            printf("epoll failure\n");
            break;
        }

        for (int i = 0; i < number; i++) {
            int sockfd = events[i].data.fd;
            if (sockfd == listenfd) {
                struct sockaddr_in client_address;
                socklen_t client_addresslen = sizeof(client_address);
                int connfd = accept(sockfd, (struct sockaddr*)&client_address, &client_addresslen);
                addfd(epollfd, connfd);
            }
            else if (sockfd == udpfd) {
                char buf[UDP_BUFFER_SIZE];
                memset(buf, '\0', UDP_BUFFER_SIZE);
                struct sockaddr_in client_address;
                socklen_t client_addresslen = sizeof(client_address);

                ret = recvfrom(udpfd, buf, UDP_BUFFER_SIZE - 1, 0, (struct sockaddr*)&client_address, &client_addresslen);

                if (ret > 0) {
                    sendto(udpfd, buf, UDP_BUFFER_SIZE - 1, 0, (struct sockaddr*)&client_address, client_addresslen);
                }
            }
            else if (events[i].events & EPOLLIN) {
                char buf[TCP_BUFFER_SIZE];
                while (1) {
                    memset(buf, '\0', TCP_BUFFER_SIZE);
                    ret = recv(sockfd, buf, TCP_BUFFER_SIZE - 1, 0);
                    if (ret < 0) {
                        if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
                            break;
                        }
                        close(sockfd);
                        break;
                    }
                    else if (ret == 0) {
                        close(sockfd);
                    }
                    else {
                        send(sockfd, buf, ret, 0);
                    }
                }
            }
            else {
                printf("something else happened\n");
            }
        }
    }
    close(listenfd);
    return 0;
}