Libevent 代码在 OSX Mountain Lion 上未连接或超时
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【中文标题】Libevent 代码在 OSX Mountain Lion 上未连接或超时【英文标题】：Libevent code not connecting or timing out on OSX Mountain Lion 【发布时间】：2013-10-14 16:00:35 【问题描述】：编辑：这是在 OSX 上运行程序时的 tcpdump 输出：
Matthew-Mitchell:calm-ocean-4924 matt$ sudo tcpdump -X -i lo0 'port 45564'
Password:
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo0, link-type NULL (BSD loopback), capture size 65535 bytes
22:52:41.620969 IP localhost.53685 > localhost.45564: Flags [S], seq 3787197032, win 65535, options [mss 16344,nop,wscale 4,nop,nop,TS val 465807577 ecr 0,sackOK,eol], length 0
0x0000: 4500 0040 ba9e 4000 4006 0000 7f00 0001 E..@..@.@.......
0x0010: 7f00 0001 d1b5 b1fc e1bc 0a68 0000 0000 ...........h....
0x0020: b002 ffff fe34 0000 0204 3fd8 0103 0304 .....4....?.....
0x0030: 0101 080a 1bc3 a8d9 0000 0000 0402 0000 ................
22:52:41.621062 IP localhost.45564 > localhost.53685: Flags [S.], seq 1362049502, ack 3787197033, win 65535, options [mss 16344,nop,wscale 4,nop,nop,TS val 465807577 ecr 465807577,sackOK,eol], length 0
0x0000: 4500 0040 8dac 4000 4006 0000 7f00 0001 E..@..@.@.......
0x0010: 7f00 0001 b1fc d1b5 512f 39de e1bc 0a69 ........Q/9....i
0x0020: b012 ffff fe34 0000 0204 3fd8 0103 0304 .....4....?.....
0x0030: 0101 080a 1bc3 a8d9 1bc3 a8d9 0402 0000 ................
22:52:41.621075 IP localhost.53685 > localhost.45564: Flags [.], ack 1, win 9186, options [nop,nop,TS val 465807577 ecr 465807577], length 0
0x0000: 4500 0034 fdb1 4000 4006 0000 7f00 0001 E..4..@.@.......
0x0010: 7f00 0001 d1b5 b1fc e1bc 0a69 512f 39df ...........iQ/9.
0x0020: 8010 23e2 fe28 0000 0101 080a 1bc3 a8d9 ..#..(..........
0x0030: 1bc3 a8d9 ....
22:52:41.621086 IP localhost.45564 > localhost.53685: Flags [.], ack 1, win 9186, options [nop,nop,TS val 465807577 ecr 465807577], length 0
0x0000: 4500 0034 53bf 4000 4006 0000 7f00 0001 E..4S.@.@.......
0x0010: 7f00 0001 b1fc d1b5 512f 39df e1bc 0a69 ........Q/9....i
0x0020: 8010 23e2 fe28 0000 0101 080a 1bc3 a8d9 ..#..(..........
0x0030: 1bc3 a8d9
我有一个相当大的库，其中包含一些使用 libevent 的网络代码。很长一段时间以来，这一直有效，但最近一些使用网络代码的较新代码很少起作用，因为无法建立连接。此外，连接超时事件也不会被触发，尽管连接永远不会完成（它应该完成）。我试图分开代码来举例说明这不起作用。以下代码在 OSX Mountain Lion 上不起作用（至少）：
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <event2/event.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#ifdef SO_NOSIGPIPE
#define CB_NOSIGPIPE true
#else
#define CB_NOSIGPIPE false
#define SO_NOSIGPIPE 0
#endif
void loopErr(void * vself);
void loopErr(void * vself)
printf("Loop error\n");
exit(EXIT_FAILURE);
void timeout(void * vself, void * foo);
void timeout(void * vself, void * foo)
printf("Timeout\n");
exit(EXIT_FAILURE);
void didConnect(void * vself, void * foo);
void didConnect(void * vself, void * foo)
printf("Did connect\n");
bool CBSocketAccept(int sock, int * connectionSock);
bool CBSocketAccept(int sock, int * connectionSock)
*connectionSock = accept(sock, NULL, NULL);
if (*connectionSock == -1)
return false;
// Make socket non-blocking
evutil_make_socket_nonblocking(*connectionSock);
// Stop SIGPIPE
int i = 1;
if (CB_NOSIGPIPE)
setsockopt(*connectionSock, SOL_SOCKET, SO_NOSIGPIPE, &i, sizeof(i));
return true;
void acceptConn(void * vself, int socket);
void acceptConn(void * vself, int socket)
int connSock;
if (! CBSocketAccept(socket, &connSock))
printf("Unable to accept a connection.\n");
exit(EXIT_FAILURE);
printf("Did accept\n");
typedef struct
struct event_base * base;
void (*onError)(void *);
void (*onTimeOut)(void *, void *); /**< Callback for timeouts */
void * communicator;
pthread_t loopThread; /**< The thread for the event loop. */
void (*userCallback)(void *);
void * userArg;
CBEventLoop;
union CBOnEvent
void (*i)(void *, int);
void (*ptr)(void *, void *);
;
typedef struct
CBEventLoop * loop; /**< For getting timeout CBLogError */
struct event * event; /**< libevent event. */
union CBOnEvent onEvent;
void * peer;
CBEvent;
void * CBStartEventLoop(void * vloop);
void * CBStartEventLoop(void * vloop)
CBEventLoop * loop = vloop;
// Start event loop
printf("Starting network event loop.\n");
if(event_base_dispatch(loop->base) == -1)
// Error
loop->onError(loop->communicator);
return NULL;
// Break from loop. Free everything.
event_base_free(loop->base);
free(loop);
return NULL;
void event_base_add_virtual(struct event_base *);
bool CBNewEventLoop(CBEventLoop ** loop, void (*onError)(void *), void (*onDidTimeout)(void *, void *), void * communicator);
bool CBNewEventLoop(CBEventLoop ** loop, void (*onError)(void *), void (*onDidTimeout)(void *, void *), void * communicator)
struct event_base * base = event_base_new();
// Create dummy event to maintain loop.
event_base_add_virtual(base);
// Create arguments for the loop
*loop = malloc(sizeof(**loop));
(*loop)->base = base;
(*loop)->onError = onError;
(*loop)->onTimeOut = onDidTimeout;
(*loop)->communicator = communicator;
// Create thread
pthread_create(&(*loop)->loopThread, NULL, CBStartEventLoop, *loop);
return loop;
bool CBSocketBind(int * sock, bool IPv6, uint16_t port);
bool CBSocketBind(int * sock, bool IPv6, uint16_t port)
struct addrinfo hints, *res, *ptr;
// Set hints for the computer's addresses.
memset(&hints, 0, sizeof(hints));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = IPv6 ? AF_INET6 : AF_INET;
hints.ai_socktype = SOCK_STREAM;
// Get host for listening
char portStr[6];
sprintf(portStr, "%u", port);
if (getaddrinfo(NULL, portStr, &hints, &res))
return false;
// Attempt to bind to one of the addresses.
for(ptr = res; ptr != NULL; ptr = ptr->ai_next)
if ((*sock = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol)) == -1)
continue;
// Prevent EADDRINUSE
int opt = 1;
setsockopt(*sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
if (bind(*sock, ptr->ai_addr, ptr->ai_addrlen) == -1)
printf("Bind gave the error %s for address on port %u.\n", strerror(errno), port);
evutil_closesocket(*sock);
continue;
break; // Success.
freeaddrinfo(res);
if (ptr == NULL) // Failure
return false;
// Prevent SIGPIPE
int i = 1;
setsockopt(*sock, SOL_SOCKET, SO_NOSIGPIPE, &i, sizeof(i));
// Make socket non-blocking
evutil_make_socket_nonblocking(*sock);
return true;
void CBCanAccept(evutil_socket_t sock, short eventNum, void * arg);
void CBCanAccept(evutil_socket_t sock, short eventNum, void * arg)
CBEvent * event = arg;
event->onEvent.i(event->loop->communicator, sock);
bool CBSocketCanAcceptEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onCanAccept)(void *, int));
bool CBSocketCanAcceptEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onCanAccept)(void *, int))
*event = malloc(sizeof(**event));
(*event)->loop = loop;
(*event)->onEvent.i = onCanAccept;
(*event)->event = event_new((*event)->loop->base, sock, EV_READ|EV_PERSIST, CBCanAccept, *event);
return true;
bool CBSocketAddEvent(CBEvent * event, uint32_t timeout);
bool CBSocketAddEvent(CBEvent * event, uint32_t timeout)
int res;
if (timeout)
uint32_t secs = timeout / 1000;
struct timeval time = secs, (timeout - secs*1000) * 1000;
res = event_add(event->event, &time);
else
res = event_add(event->event, NULL);
return ! res;
bool CBNewSocket(int * sock, bool IPv6);
bool CBNewSocket(int * sock, bool IPv6)
// You need to use PF_INET for IPv4 mapped IPv6 addresses despite using the IPv6 format.
*sock = socket(IPv6 ? PF_INET6 : PF_INET, SOCK_STREAM, 0);
if (*sock == -1)
return false;
// Stop SIGPIPE annoying us.
int i = 1;
if (CB_NOSIGPIPE)
setsockopt(*sock, SOL_SOCKET, SO_NOSIGPIPE, &i, sizeof(i));
// Make address reusable
setsockopt(*sock, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(i));
// Make socket non-blocking
evutil_make_socket_nonblocking(*sock);
return true;
bool CBSocketConnect(int sock, uint8_t * IP, bool IPv6, uint16_t port);
bool CBSocketConnect(int sock, uint8_t * IP, bool IPv6, uint16_t port)
// Create sockaddr_in6 information for a IPv6 address
int res;
if (IPv6)
struct sockaddr_in6 address;
memset(&address, 0, sizeof(address)); // Clear structure.
address.sin6_family = AF_INET6;
memcpy(&address.sin6_addr, IP, 16); // Move IP address into place.
address.sin6_port = htons(port); // Port number to network order
res = connect(sock, (struct sockaddr *)&address, sizeof(address));
else
struct sockaddr_in address;
memset(&address, 0, sizeof(address)); // Clear structure.
address.sin_family = AF_INET;
memcpy(&address.sin_addr, IP + 12, 4); // Move IP address into place. Last 4 bytes for IPv4.
address.sin_port = htons(port); // Port number to network order
res = connect(sock, (struct sockaddr *)&address, sizeof(address));
if (res < 0 && errno == EINPROGRESS)
return true;
return false;
void CBDidConnect(evutil_socket_t socketID, short eventNum, void * arg);
void CBDidConnect(evutil_socket_t socketID, short eventNum, void * arg)
CBEvent * event = arg;
if (eventNum & EV_TIMEOUT)
// Timeout for the connection
event->loop->onTimeOut(event->loop->communicator, event->peer);
else
int optval = -1;
socklen_t optlen = sizeof(optval);
getsockopt(socketID, SOL_SOCKET, SO_ERROR, &optval, &optlen);
if (optval)
// Act as timeout
printf("Connection error: %s\n", strerror(optval));
event->loop->onTimeOut(event->loop->communicator, event->peer);
else
// Connection successful
event->onEvent.ptr(event->loop->communicator, event->peer);
bool CBSocketDidConnectEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onDidConnect)(void *, void *), void * peer);
bool CBSocketDidConnectEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onDidConnect)(void *, void *), void * peer)
*event = malloc(sizeof(**event));
(*event)->loop = loop;
(*event)->onEvent.ptr = onDidConnect;
(*event)->peer = peer;
(*event)->event = event_new((*event)->loop->base, sock, EV_TIMEOUT|EV_WRITE, CBDidConnect, *event);
return true;
int main(int argc, const char * argv[])
int listeningSocket, connSocket;
CBEvent *acceptEvent, *connectEvent;
CBEventLoop *listeningEventLoop, *connEventLoop;
if (!CBNewEventLoop(&listeningEventLoop, loopErr, timeout, NULL)
|| !CBNewEventLoop(&connEventLoop, loopErr, timeout, NULL))
printf("Unable to start event loops.");
return EXIT_FAILURE;
if (!CBSocketBind(&listeningSocket, false, 45564))
printf("Unable to bind a socket for listening");
return EXIT_FAILURE;
if (!CBSocketCanAcceptEvent(&acceptEvent, listeningEventLoop, listeningSocket, acceptConn))
printf("Unable to create an accept event");
return EXIT_FAILURE;
if(!CBSocketAddEvent(acceptEvent, 0))
printf("Unable to add an accept event\n");
return EXIT_FAILURE;
if (listen(listeningSocket, 1) == -1)
printf("Unable to start listening\n");
return EXIT_FAILURE;
// Make socket
if (!CBNewSocket(&connSocket, false))
printf("Socket create fail\n");
return EXIT_FAILURE;
// Add event for connection
if (!CBSocketDidConnectEvent(&connectEvent, connEventLoop, connSocket, didConnect, NULL))
printf("Couldn't create did connect event\n");
return EXIT_FAILURE;
if (!CBSocketAddEvent(connectEvent, 1000))
printf("Couldn't add connect event\n");
return EXIT_FAILURE;
// Connect
if (!CBSocketConnect(connSocket, (uint8_t [])0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 127, 0, 0, 1, false, 45564))
printf("Couldn't connect\n");
return EXIT_FAILURE;
pthread_exit(NULL);
return 0;
当我运行它时，我得到：
Starting network event loop.
Starting network event loop.
没有别的了。没有连接可以接受，没有超时，什么都没有。但是我可以确认这在 Linux Mint 13 上确实有效。我也尝试了不同的端口号，但没有运气。
编辑：看来我遇到了与 libev 类似的问题。我刚刚尝试用 libev 重新实现代码，我遇到了同样的问题。不过，我还没有尝试将上面的小示例更改为 libev。
【问题讨论】：
【参考方案1】：这段代码有几个问题。
首先，CBNewEventLoop 总是返回 true，因为它返回 (bool)loop（这是 main 中堆栈变量之一的地址）。此外，您似乎可以通过返回 (bool)(*loop) 检测到的唯一错误是 malloc 失败，但如果 malloc 失败，您需要在写入 *loop 之前检查其结果。
其次，更根本的是，您在一个线程中运行一个事件循环，并从主线程调用它的方法。事件驱动系统通常不是线程安全的。您应该将此代码构建为一系列回调，以便在事件循环的线程上运行。
最后，一次需要多个事件循环的情况很少见。您应该为该进程创建一个事件循环，并将其用于侦听和连接。
【讨论】：
感谢您的回答。您的第一点是正确的，但这与这个问题无关。但是，您的第二点是正确的。我忘记使用evthread_use_pthreads(); 我需要调用它以使 libevent 函数成为线程安全的，从而允许我在主线程中建立连接。我当然可以在网络线程中做到这一点。我有两个事件循环的原因是因为这是一个测试，而不是一个实际的应用程序。
与 Ben 的最后一点相反，在多核机器上运行（服务器）应用程序时，需要多个事件循环以获取尽可能高的性能。尝试在 8 核机器上运行单个事件循环与在 8 个事件循环上运行，您会看到巨大的差异。
好点@Corehacker；我已经习惯了 Python 世界，线程并不是真正的解决方案，每个进程必须有一个事件循环，但在 C 中，你可以使用线程而不是进程并获得相同的结果。以上是关于Libevent 代码在 OSX Mountain Lion 上未连接或超时的主要内容，如果未能解决你的问题，请参考以下文章
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