C语言 连接（函数）错误上的操作现在正在进行错误
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Operation now in progress error on connect( function) error
提问by iyasar
I want to set timeout value of function connect but I get this error: "Operation now in progress"
我想设置函数连接的超时值，但出现此错误：“操作正在进行中”
My code:
我的代码：
if ((he = gethostbyname(authdefhost)) == NULL) {
snprintf(errbuf, CERRBUFSIZ - 1, "cannot resolve %s: %s\n", authdefhost, hstrerror(h_errno));
return -1;
}
sin.sin_family = AF_INET;
memcpy(&sin.sin_addr, he->h_addr_list[0], sizeof(struct in_addr));
if ((sd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
snprintf(errbuf, CERRBUFSIZ - 1, "cannot create client socket: %s\n", strerror(errno));
return -1;
}
if ((fcntl(sd, F_SETFL, O_NONBLOCK) < 0))
printf("error on setting socket flags.");
if (connect(sd, (void *) & sin, sizeof(sin)) == -1) {
snprintf(errbuf, CERRBUFSIZ - 1, "cannot connect to server %s: %s\n", authdefhost, strerror(errno));
close(sd);
return -1;
}
FD_ZERO(&fdset);
FD_SET(sd, &fdset);
int rv;
if ((rv = select(sd + 1, NULL, &fdset, NULL, &tv)) == -1) {
printf("error occurred on select function.");
return -1;
}
else if (rv == 0) {
printf("time out occurred.");
return -1;
}
else {
printf("connection established");
return sd;
}
回答by ninjalj
When you call connect()on a non-blocking socket, you'll get EINPROGRESSinstead of blocking waiting for the connection handshake to complete. Then, you have to select()for writability, and check the socket error to see if the connection has completed.
当您调用connect()非阻塞套接字时，您将获得EINPROGRESS而不是阻塞等待连接握手完成。然后，您必须select()为了可写性，并检查套接字错误以查看连接是否已完成。
From Linux's connect()manpage:
从 Linux 的connect()联机帮助页：
EINPROGRESS
The socket is nonblocking and the connection cannot be completed
immediately. It is possible to select(2) or poll(2) for completion by
selecting the socket for writing. After select(2) indicates
writability, use getsockopt(2) to read the SO_ERROR option at level
SOL_SOCKET to determine whether connect() completed successfully
(SO_ERROR is zero) or unsuccessfully (SO_ERROR is one of the usual
error codes listed here, explaining the reason for the failure).
EINPROGRESS
The socket is nonblocking and the connection cannot be completed
immediately. It is possible to select(2) or poll(2) for completion by
selecting the socket for writing. After select(2) indicates
writability, use getsockopt(2) to read the SO_ERROR option at level
SOL_SOCKET to determine whether connect() completed successfully
(SO_ERROR is zero) or unsuccessfully (SO_ERROR is one of the usual
error codes listed here, explaining the reason for the failure).
