我正在尝试使用epoll来实现套接字服务器。我有2个线程执行2个任务：
对于我的测试，我将客户端和服务器放在同一台机器上，运行3或4个客户端。
服务器工作正常，直到我没有通过发出CTRL-C来杀死其中一个客户端：一旦我这样做，服务器开始循环并以非常快的速率从其他客户端打印数据。奇怪的是那个
epoll_wait也应该在其中一个客户端断开连接时打印，因为它也检查EPOLLHUP或EPOLLERR epoll_wait应该在打印前稍等一下，因为我给了他3000毫秒的超时时间。非常感谢
的Mn
// server.cpp
#include <iostream>
#include <cstdio>
#include <cstring>
extern "C" {
#include <sys/epoll.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <pthread.h>
}
#define MAX_BACKLOG 10
void* readerthread(void* args){
int epfd = *((int*)args);
epoll_event outwait[10];
while(true){
int retpw = epoll_wait( epfd, outwait,20, 3000 );
if( retpw == -1 ){
printf("epoll error %m\n");
}else if( retpw == 0 ){
printf("nothing is ready yet\n");
continue;
}else{
for( int i=0;i<retpw;i++){
if( outwait[i].events & EPOLLIN ){
int fd = outwait[i].data.fd;
char buf[64];
if( -1 == read(fd,buf,64) ){
printf("error reading %m\n");
}
printf("%s\n",buf);
}else{
std::cout << "other event" << std::endl;
}
}
}
}
}
int main(){
int epfd = epoll_create(10);
if( -1 == epfd ){
std::cerr << "error creating EPOLL server" << std::endl;
return -1;
}
pthread_t reader;
int rt = pthread_create( &reader, NULL, readerthread, (void*)&epfd );
if( -1 == rt ){
printf("thread creation %m\n");
return -1;
}
struct addrinfo addr;
memset(&addr,0,sizeof(addrinfo));
addr.ai_family = AF_INET;
addr.ai_socktype = SOCK_STREAM;
addr.ai_protocol = 0;
addr.ai_flags = AI_PASSIVE;
struct addrinfo * rp,* result;
getaddrinfo( "localhost","59000",&addr,&result );
for( rp = result; rp != NULL; rp = rp->ai_next ){
// we want to take the first ( it could be IP_V4
// or IP_V6 )
break;
}
int sd = socket( AF_INET, SOCK_STREAM, 0 );
if(-1==sd ){
std::cerr << "error creating the socket" << std::endl;
return -1;
}
// to avoid error 'Address already in Use'
int optval = 1;
setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
if( -1==bind( sd, result->ai_addr, result->ai_addrlen ) ){
printf("%m\n");
std::cerr << "error binding" << std::endl;
return -1;
}
while(true){
std::cout << "listen" << std::endl;
if( -1== listen(sd, MAX_BACKLOG ) ){
std::cerr << "listen didn't work" << std::endl;
return -1;
}
std::cout << "accept" << std::endl;
sockaddr peer;
socklen_t addr_size;
int pfd = accept( sd, &peer ,&addr_size );
if( pfd == -1 ){
std::cerr << "error calling accept()" << std::endl;
return -1;
}
epoll_event ev;
ev.data.fd = pfd;
ev.events = EPOLLIN;
std::cout << "adding to epoll list" << std::endl;
if( -1 == epoll_ctl( epfd, EPOLL_CTL_ADD, pfd, &ev ) ){
printf("epoll_ctl error %m\n");
return -1;
}
}
}
// end of server.cpp
// client.cpp
#include <iostream>
#include <cstring>
#include <cstdio>
extern "C"{
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
}
int main(){
const char* servername = "localhost";
const char* serverport = "59000";
struct addrinfo server_address;
memset( &server_address, 0, sizeof(struct addrinfo) );
server_address.ai_family = AF_INET;
server_address.ai_socktype = SOCK_STREAM;
server_address.ai_protocol = 0; // any protocol
server_address.ai_flags = 0;
struct addrinfo * result, * rp;
int res = getaddrinfo( servername, serverport, &server_address, &result );
if( -1 == res ){
std::cout << "I cannot getaddress " << servername << std::endl;
return -1;
}
int fd = socket( server_address.ai_family
, server_address.ai_socktype
, server_address.ai_protocol );
if( -1 == fd ){
printf("I cannot open a socket %m\n");
return -1;
}
for( rp = result; rp != NULL; rp = rp->ai_next ){
std::cout << "************" << std::endl;
if( -1 == connect( fd, rp->ai_addr, rp->ai_addrlen ) ){
close(fd);
}else{
std::cout << "connected" << std::endl;
break;
}
}
if( rp == NULL ){
std::cerr << "I couldn't connect server " << servername << std::endl;
}
while(true){
sleep(2);
pid_t me = getpid();
char buf[64];
bzero( buf,sizeof(buf));
sprintf( buf,"%ld",me );
write(fd,buf,sizeof(buf));
printf("%s\n",buf);
}
}
// end of client.cpp
答案 0 :(得分：3)
另一方彻底关闭的插座将变得可读，read(2)将返回0，您必须检查它。现在编码 - 级别触发的轮询 - epoll_wait(2)每次都返回，而不会等待您仍然没有读取该流末尾。
或者，您可以切换到边缘触发的轮询（EPOLLET）并对EPOLLRDHUP做出反应。
答案 1 :(得分：3)
客户端断开连接由文件描述符上的EOF条件发出信号。系统认为EOF是文件描述符“可读”的状态。但是，当然，无法读取EOF条件。这是循环的来源。 epoll的作用类似于断开连接的客户端的文件描述符始终可读。您可以通过检查read何时返回0字节读取来检测您是否具有EOF条件。
处理EOF条件的唯一方法是以某种方式close文件描述符。具体取决于事物的流向，可能是shutdown(sockfd, SHUT_RD)，shutdown(sockfd, SHUT_RDWR)或close(sockfd);。
除非您因任何原因知道需要shutdown(2)来电，否则我建议您使用close。当然，您应该记得在epoll之前告诉close文件描述符不再受关注。我不确定如果你不这样做会发生什么，但有一种可能性是epoll会出错。另一个是epoll将神秘地开始报告具有相同数值的新文件描述符的事件，然后再将其添加到列表epoll应关注的内容。