connect - 发起连接在套接字上
内容简介
#include#include int connect(int sockfd, const struct sockaddr *serv_addr, socklen_t addrlen)
描述
The%uA0connect() system call connects the socket referred to by the file descriptor%uA0sockfd%uA0to the address specified by%uA0serv_addr. The%uA0addrlen%uA0argument specifies the size of%uA0serv_addr. The format of the address in%uA0serv_addr%uA0is determined by the address space of the socket%uA0sockfd see%uA0socket(2) for further details.
If the socket%uA0sockfd%uA0is of type%uA0SOCK_DGRAM%uA0then%uA0serv_addr%uA0is the address to which datagrams are sent by default, and the only address from which datagrams are received. If the socket is of type%uA0SOCK_STREAM%uA0or%uA0SOCK_SEQPACKET, this call attempts to make a connection to the socket that is bound to the address specified byserv_addr.
Generally, connection-based protocol sockets may successfully%uA0connect() only once connectionless protocol sockets may use%uA0connect() multiple times to change their association. Connectionless sockets may dissolve the association by connecting to an address with the%uA0sa_family%uA0member of%uA0sockaddr%uA0set to%uA0AF_UNSPEC.
返回值
如果连接或绑定成功，则返回0。上的错误，则返回-1，anderrno设置适当。
错误
以下是一般的套接字错误。有可能是其他域特定的错误代码。
| Error Code | 描述 |
|---|---|
| EACCES | For Unix domain sockets, which are identified by pathname: Write permission is denied on the socket file, or search permission is denied for one of the directories in the path prefix. (See also%uA0path_resolution(2).) |
| EACCES, EPERM | The user tried to connect to a broadcast address without having the socket broadcast flag enabled or the connection request failed because of a local firewall rule. |
| EADDRINUSE | Local address is already in use. |
| EAFNOSUPPORT | The passed address didn’t have the correct address family in itssa_family%uA0field. |
| EADDRNOTAVAIL | Non-existent interface was requested or the requested address was not local. |
| EALREADY | The socket is non-blocking and a previous connection attempt has not yet been completed. |
| EBADF | The file descriptor is not a valid index in the descriptor table. |
| ECONNREFUSED | No one listening on the remote address. |
| EFAULT | The socket structure address is outside the user’s address space. |
| EINPROGRESS | The socket is non-blocking and the connection cannot be completed immediately. It is possible to%uA0select(2) or%uA0poll(2) for completion by selecting the socket for writing. After%uA0select(2) indicates writability, use%uA0getsockopt(2) to read the%uA0SO_ERRORoption at level%uA0SOL_SOCKET%uA0to determine whether%uA0connect() completed successfully (SO_ERROR%uA0is zero) or unsuccessfully (SO_ERROR%uA0is one of the usual error codes listed here, explaining the reason for the failure). |
| EINTR | The system call was interrupted by a signal that was caught. |
| EISCONN | The socket is already connected. |
| ENETUNREACH | Network is unreachable. |
| ENOTSOCK | The file descriptor is not associated with a socket. |
| ETIMEDOUT | Timeout while attempting connection. The server may be too busy to accept new connections. Note that for IP sockets the timeout may be very long when syncookies are enabled on the server. |
遵循于
SVr4, 4.4BSD (the%uA0connect() function first appeared in 4.2BSD).
注意
The third argument of%uA0connect() is in reality an%uA0int%uA0(and this is what 4.x BSD and libc4 and libc5 have). Some POSIX confusion resulted in the present%uA0socklen_t, also used by glibc. See also%uA0accept(2).
BUGS
Unconnecting a socket by calling%uA0connect() with a%uA0AF_UNSPECꂭdress is not yet implemented.