操作现在在连接（函数）进度的错误错误

Question

我想设置的功能超时值连接，但我得到这个错误：“操作正在进行”

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; 
} 

Answer 1

当您在非阻塞套接字上调用connect()，您将获得EINPROGRESS而不是阻止等待连接握手完成。然后，您必须为select()提供可写性，并检查套接字错误以查看连接是否已完成。

从Linux的connect() manpage：

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).