09-24-2012
Correct approach is after calling connect() to check if errno is set to EINPROGRESS and if so use select() to see when socket can be written to, also its best not to loop 5 times but set a single timeout since your select() will fire up when socket would change state (in relation to connect()) right away and you re just wasting CPU cycles. Keep in mind that kernel has internal timeout maximum set for TCP handshakes that is somewhere 1-2mins after that connect() should return ETIMEDOUT no matter what you do and only then you would need to have to implement a loop.
Edit:
If your connect() fails at first run then your problem is not in non-blocking sockets, but on receiving end or somewhere in between or maybe you set up 'struct sockaddr sin' incorrectly.
Last edited by expl; 09-24-2012 at 06:49 AM..
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LEARN ABOUT NETBSD
connect
CONNECT(2) BSD System Calls Manual CONNECT(2)
NAME
connect -- initiate a connection on a socket
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/socket.h>
int
connect(int s, const struct sockaddr *name, socklen_t namelen);
DESCRIPTION
The parameter s is a socket. If it is of type SOCK_DGRAM, this call specifies the peer with which the socket is to be associated; this
address is that to which datagrams are to be sent, and the only address from which datagrams are to be received. If the socket is of type
SOCK_STREAM, this call attempts to make a connection to another socket. The other socket is specified by name, which is an address in the
communications space of the socket. namelen indicates the amount of space pointed to by name, in bytes. Each communications space inter-
prets the name parameter in its own way. Generally, stream sockets may successfully connect() only once; datagram sockets may use connect()
multiple times to change their association. Datagram sockets may dissolve the association by connecting to an invalid address, such as a
null address.
If a connect() call is interrupted by a signal, it will return with errno set to EINTR and the connection attempt will proceed as if the
socket was non-blocking. Subsequent calls to connect() will set errno to EALREADY.
RETURN VALUES
If the connection or binding succeeds, 0 is returned. Otherwise a -1 is returned, and a more specific error code is stored in errno.
ERRORS
The connect() call fails if:
[EBADF] s is not a valid descriptor.
[ENOTSOCK] s is a descriptor for a file, not a socket.
[EADDRNOTAVAIL] The specified address is not available on this machine.
[EAFNOSUPPORT] Addresses in the specified address family cannot be used with this socket.
[EISCONN] The socket is already connected.
[ETIMEDOUT] Connection establishment timed out without establishing a connection.
[ECONNREFUSED] The attempt to connect was forcefully rejected.
[ENETUNREACH] The network isn't reachable from this host.
[EADDRINUSE] The address is already in use.
[EFAULT] The name parameter specifies an area outside the process address space.
[EINPROGRESS] The socket is non-blocking and the connection cannot be completed immediately. It is possible to select(2) or poll(2) for
completion by selecting or polling the socket for writing. The success or failure of the connect operation may be deter-
mined by using getsockopt(2) to read the socket error status with the SO_ERROR option at the SOL_SOCKET level. The
returned socket error status is zero on success, or one of the error codes listed here on failure.
[EALREADY] Either the socket is non-blocking mode or a previous call to connect() was interrupted by a signal, and the connection
attempt has not yet been completed.
[EINTR] The connection attempt was interrupted by a signal.
The following errors are specific to connecting names in the UNIX domain. These errors may not apply in future versions of the UNIX IPC
domain.
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
[ENOENT] The named socket does not exist.
[EACCES] Search permission is denied for a component of the path prefix, or write access to the named socket is denied.
[ELOOP] Too many symbolic links were encountered in translating the pathname.
SEE ALSO
accept(2), getsockname(2), getsockopt(2), poll(2), select(2), socket(2)
HISTORY
The connect() function call appeared in 4.2BSD.
BSD
May 18, 2004 BSD