WSAEventSelect模型“Ctrl+C”是否能关闭掉服务端？

[qingdujun]

大家好！我遇到一个很奇怪的问题。我尝试着使用`WSAEventSelect `写了一个回射服务端。再写了一个客户端程序，去连接它。

一切都正常。

然后奇怪的是，当我对服务端exe使用“Ctrl+C”时，客户端并没有任何反应？此时，我在客户端上发任何字符串，还是能被回射过来。

我索性直接把服务端exe退出了，这时候我想着客户端应该也挂掉了吧？

奇怪的是，客户端的数据还能被回射。

---------------

我也几乎能确定服务端确实是退出了，因为我新启一个客户端，无法连接到服务端。

但是，原来连上去的客户端，并没有因为服务端的关闭而受影响？很奇怪。

源代码1：服务端程序

#include <WinSock2.h>
#include <stdio.h>

#pragma comment(lib,"ws2_32.lib") 

#define SERV_PORT 9527
#define MAXLINE 128
#define LISTENQ 5
#define MAXBUFSIZE 1024

void exit_msg(const char* msg) {
	perror(msg);
	exit(0);
}

int main(int argc, char* argv[]) {
	int listenfd, connfd, cevents, idx, clilen, i, n;
	struct sockaddr_in cliaddr, servaddr;
	char buf[MAXBUFSIZE];
	WSAEVENT event, wsaevents[WSA_MAXIMUM_WAIT_EVENTS];//<WinSock2.h> #define WSA_MAXIMUM_WAIT_EVENTS 64
	WSANETWORKEVENTS net_events;
	SOCKET sockets[WSA_MAXIMUM_WAIT_EVENTS];
	WSADATA wsa;

	WSAStartup(MAKEWORD(2, 2), &wsa);

	listenfd = socket(AF_INET, SOCK_STREAM, 0);

	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);

	if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
		exit_msg("bind error");

	listen(listenfd, LISTENQ);
	//1、创建并设置WSACreateEvent
	event = WSACreateEvent();
	WSAEventSelect(listenfd, event, FD_ACCEPT | FD_CLOSE);
	cevents = 0;
	wsaevents[cevents] = event;
	sockets[cevents] = listenfd;
	++cevents;

	for (; ; ) {
		//2、WSAWaitForMultipleEvents等待事件被触发
		if ((idx = WSAWaitForMultipleEvents(cevents, wsaevents, FALSE, WSA_INFINITE, FALSE)) == WSA_WAIT_FAILED)
			exit_msg("WSA_WAIT_FAILED");
			
		if (idx == WSA_WAIT_TIMEOUT) 
			continue;

		idx -= WSA_WAIT_EVENT_0;
		//3、WSAEnumNetworkEvents获取具体发生的事件类型
		WSAEnumNetworkEvents(sockets[idx], wsaevents[idx], &net_events);
		WSAResetEvent(wsaevents[idx]);//4、设置事件为无信号状态
		if (net_events.lNetworkEvents & FD_ACCEPT) {
			puts("FD_ACCEPT");
			if (net_events.iErrorCode[FD_ACCEPT_BIT] == 0) {
				if (cevents >= WSA_MAXIMUM_WAIT_EVENTS)
					exit_msg("too many clients");
				clilen = sizeof(cliaddr);
				connfd = accept(sockets[idx], (struct sockaddr*)&cliaddr, &clilen);
				event = WSACreateEvent();
				WSAEventSelect(connfd, event, FD_READ | FD_WRITE | FD_CLOSE);
				wsaevents[cevents] = event;
				sockets[cevents] = connfd;
				++cevents;
			}
		}
		if (net_events.lNetworkEvents & FD_READ) {
			puts("FD_READ");
			if (net_events.iErrorCode[FD_READ_BIT] == 0) {
				if ((n = recv(sockets[idx], buf, MAXBUFSIZE, 0)) != 0) 
					send(sockets[idx], buf, n, 0); //TODO: send + while
			}
		}
		if (net_events.lNetworkEvents & FD_WRITE) {
			puts("FD_WRITE");
			if (net_events.iErrorCode[FD_WRITE_BIT] == 0)
				printf("FD_WRITE...(%d)\n", sockets[idx]);
		}
		
		if (net_events.lNetworkEvents & FD_CLOSE) {
			puts("FD_CLOSE");
			if (net_events.iErrorCode[FD_CLOSE_BIT] == 0) {
				closesocket(sockets[idx]);
				WSACloseEvent(wsaevents[idx]);//5、释放事件所占用的资源
				for (i = idx; i < cevents - 1; ++i) { 
					wsaevents[i] = wsaevents[i + 1];
					sockets[i] = sockets[i + 1];
				}
				--cevents;
			}
		}
	}

	WSACleanup();

	return 0;
}

源代码2：客户端程序

#include <windows.h>
#include <stdio.h>

#pragma comment(lib,"ws2_32.lib") 

#define SERV_PORT 9527
#define MAXLINE 128

void exit_msg(const char* msg) {
	perror(msg);
	exit(0);
}

void str_cli(FILE* fp, int sockfd) {
	char buf[MAXLINE];
	while (fgets(buf, MAXLINE, fp) != NULL) {
		int n = send(sockfd, buf, strlen(buf), 0);
		if (recv(sockfd, buf, MAXLINE, 0) == 0)
			exit_msg("str_cli readline==0");
		fputs(buf, stdout);
	}
}

int main(int argc, char* argv[]) {
	SOCKET sockfd;
	WSADATA wsa;
	struct sockaddr_in servaddr;

	/*if (argc != 2)
	exit_msg("argv != 2");*/

	WSAStartup(MAKEWORD(2, 2), &wsa);

	sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_port = htons(SERV_PORT);
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.S_un.S_addr = inet_addr(/*argv[1]*/"127.0.0.1");

	if (connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
		exit_msg("connect error !");
	}

	str_cli(stdin, sockfd);

	closesocket(sockfd);
	WSACleanup();

	return 0;
}

[qingdujun]

我在群里@稀饭 帮忙发现了问题，是一个recv值处理的错误。

只有正常关闭socket，recv才会返回0。其他异常情况下会返回<0的值。