03-29-2011
Help with sockets in C
if i have a server which wants to connect to exactly 5 clients, does that mean i need 5 socket file descriptors and use
listen(socket_fd,1);
for each one
or just do
listen(socket_fd,5)
also whats the second parameter number mean? what happens if i put 0 there?
also if i am connected to five clients, and i have listen(socket_fd,5), does that mean while one of the 5 is being handled, it has support for the other 4 to continue waiting?, or I am not sure what its doing here, can I even put a 0 there, if I have 5 clients connected, will that work?
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LEARN ABOUT OSX
getpeereid
GETPEEREID(3) BSD Library Functions Manual GETPEEREID(3)
NAME
getpeereid -- get the effective credentials of a UNIX-domain peer
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
int
getpeereid(int s, uid_t *euid, gid_t *egid);
DESCRIPTION
The getpeereid() function returns the effective user and group IDs of the peer connected to a UNIX-domain socket. The argument s must be a
UNIX-domain socket (unix(4)) of type SOCK_STREAM on which either connect(2) or listen(2) have been called. The effective used ID is placed
in euid, and the effective group ID in egid.
The credentials returned to the listen(2) caller are those of its peer at the time it called connect(2); the credentials returned to the
connect(2) caller are those of its peer at the time it called listen(2). This mechanism is reliable; there is no way for either side to
influence the credentials returned to its peer except by calling the appropriate system call (i.e., either connect(2) or listen(2)) under
different effective credentials.
One common use of this routine is for a UNIX-domain server to verify the credentials of its client. Likewise, the client can verify the cre-
dentials of the server.
IMPLEMENTATION NOTES
On FreeBSD, getpeereid() is implemented in terms of the LOCAL_PEERCRED unix(4) socket option.
RETURN VALUES
The getpeereid() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
cate the error.
ERRORS
The getpeereid() function fails if:
[EBADF] The argument s is not a valid descriptor.
[ENOTSOCK] The argument s is a file, not a socket.
[ENOTCONN] The argument s does not refer to a socket on which connect(2) or listen(2) have been called.
[EINVAL] The argument s does not refer to a socket of type SOCK_STREAM, or the kernel returned invalid data.
SEE ALSO
connect(2), getpeername(2), getsockname(2), getsockopt(2), listen(2), unix(4)
HISTORY
The getpeereid() function appeared in FreeBSD 4.6.
BSD
July 15, 2001 BSD