libevent异步TCP连接，判断是否连接成功


libevent异步TCP连接服务器的过程：

1）创建nonblock的socket，

2）调用connect连接服务器，检查返回值，判断是否是阻塞了，如果是，就设置等待 EV_WRITE事件：

     event_set(&m_evSocket, m_iSockFd, EV_WRITE, onConnect, this);

3）EV_WRITE返回后，判断event是否为EV_WRITE，

关键一点：如果EV_WRITE，还要进一步判断sockopt是否正确。

代码片段如下：

bool CClientSocket::connectSocket(string szHostAddr, int nHostPort){
if (m_iSockFd == -1){
createSocket();
}

struct sockaddr_in Ser_addr;
memset(&Ser_addr, 0, sizeof(struct sockaddr_in));

Ser_addr.sin_family = AF_INET;
Ser_addr.sin_addr.s_addr = inet_addr(szHostAddr.c_str());
Ser_addr.sin_port = htons(nHostPort);

if(connect(m_iSockFd, (const struct sockaddr *) &Ser_addr,sizeof(Ser_addr)) == -1){
if ( errno == EINPROGRESS || errno == EWOULDBLOCK){
event_set(&m_evSocket, m_iSockFd, EV_WRITE, onConnect, this);
event_base_set(&m_eventbase, &m_evSocket);
struct timeval tv1;
tv1.tv_sec = 5;
tv1.tv_usec = 0;
event_add(&m_evSocket, &tv1);
m_connSCRStatus.sockRequestSended();
printf("connect would block\n");
return true;
}
else{
printf("fail to connect\n");
closeSocket();
return false;
}
}
else{
printf("connected directly...\n");
// connected directlly
event_set(&m_evSocket, m_iSockFd, EV_READ|EV_PERSIST, onRecv, this);
event_base_set(&m_eventbase, &m_evSocket);
event_add(&m_evSocket, NULL);
onConnect();
return true;
}

}

void CClientSocket::onConnect(int fd, short event, void *arg){
CClientSocket *pThis = (CClientSocket*)arg;
if (event == EV_WRITE){
int err;
socklen_t len = sizeof(err);
getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &len);
if (err) {
printf("connect return ev_write, but check failed\n");
pThis->closeSocket();
}
else{
event_set(&pThis->m_evSocket, pThis->m_iSockFd, EV_READ|EV_PERSIST, onRecv, arg);
event_base_set(&pThis->m_eventbase, &pThis->m_evSocket);
event_add(&pThis->m_evSocket, NULL);
pThis->onConnect();
printf("connect return ev_write, check ok\n");
}
}
else{ // timeout
printf("connect return failed\n");
pThis->closeSocket();
}
}

void CClientSocket::onConnect(){
logMessage("connect ok!");
//

}


参考：

http://stackoverflow.com/questions/16074981/how-to-check-if-connection-is-established-when-use-libev-with-non-block-socket