linux网络编程十七：I/O复用的应用－同时处理TCP和UDP服务

在此之前，我们讨论的服务器程序都只监听一个端口。在实际应用中，有不少服务器程序能同时监听多个端口，比如超组服务xinet。

从bind系统调用的参数看，一个socket只能绑定一个socket地址。因此，要监听多个端口就必须创建多个socket，并绑定到各个端口上。这样一来，服务器程序就需要同时管理多个监听socket，I/O复用技术就有了用武之地。

另外，即使是同一个端口，如果服务器要同时处理该端口上TCP和UPD请求，也是需要创建两个不同的socket，并将它们都绑到该端口上。

1. 代码实现

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

#define MAX_EVENT_NUMBER 1024
#define TCP_BUFFER_SIZE 512
#define UDP_BUFFER_SIZE 1024

int setnonblocking(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;

epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
setnonblocking(fd);
}

int main(int argc, char **argv)
{
if (argc != 2) {
fprintf(stderr, "Usage: %s port\n", basename(argv[0]));
return 1;
}

int port = atoi(argv[1]);

int ret = 0;
int error;

struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
address.sin_port = htons(port);
address.sin_addr.s_addr = htonl(INADDR_ANY);

//TCP
int sockfd = socket(PF_INET, SOCK_STREAM, 0);
if (sockfd == -1)
return 1;

printf("server start...\n");

int reuse = 1;
ret = setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));
if (ret == -1) {
error = errno;
while ((close(sockfd) == -1) && (errno == EINTR));
errno = error;
return 1;
}

printf("server reuseaddr success\n");

if ((bind(sockfd, (struct sockaddr*)&address, sizeof(address)) == -1) ||
(listen(sockfd, 5) == -1)) {
error = errno;
while ((close(sockfd) == -1) && (errno == EINTR));
errno = error;
return 1;
}

printf("server bind and listen success\n");

//UDP
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
address.sin_port = htons(port);
address.sin_addr.s_addr = htonl(INADDR_ANY);

int udpfd = socket(PF_INET, SOCK_DGRAM, 0);
if (udpfd == -1) {
error = errno;
while ((close(sockfd) == -1) && (close(udpfd) == -1) &&
(errno == EINTR));
errno = error;
return 1;
}

ret = bind(udpfd, (struct sockaddr*)&address, sizeof(address));
if (ret == -1) {
error = errno;
while ((close(sockfd) == -1) && (close(udpfd) == -1) &&
(errno == EINTR));
errno = error;
return 1;
}

epoll_event events[MAX_EVENT_NUMBER];
int epollfd = epoll_create(5);
if (epollfd == -1) {
error = errno;
while ((close(sockfd) == -1) && (close(udpfd) == -1) &&
(errno == EINTR));
errno = error;
return 1;
}

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

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

for (int i = 0; i < number; i++) {
int listenfd = events[i].data.fd;
if (listenfd == sockfd) {
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);

int connfd;

while ( ((connfd = accept(sockfd, (struct sockaddr*)&client_address, &client_addrlength)) == -1) &&
(connfd == EINTR));

addfd(epollfd, connfd);
}
else if (listenfd == udpfd) {
char buf[UDP_BUFFER_SIZE];
memset(buf, '\0', UDP_BUFFER_SIZE);

struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);

ret = recvfrom(udpfd, buf, UDP_BUFFER_SIZE-1, 0, (struct sockaddr*)&client_address, &client_addrlength);
if (ret > 0)
{
sendto(udpfd, buf, UDP_BUFFER_SIZE-1, 0, (struct sockaddr*)&client_address, client_addrlength);
}
}
else if (events[i].events & EPOLLIN) {
char buf[TCP_BUFFER_SIZE];
while (1) {
memset(buf, '\0', TCP_BUFFER_SIZE);
ret = recv(listenfd, buf, TCP_BUFFER_SIZE, 0);
if (ret < 0)
{
if (errno == EAGAIN || errno == EWOULDBLOCK)
break;

close(listenfd);
break;
}
else if (ret == 0)
close(listenfd);
else
send(listenfd, buf, ret, 0);
}
}
else
{
printf("something else happened\n");
}

}

}

close(sockfd);

return 0;
}

参考：《linux高性能服务器编程》