Nonblocking I/O - HP Rp3440-4 - 9000 - 0 MB RAM Programmer's Manual

Nonblocking I/O

Sockets are created in blocking mode I/O by default. You can specify that
a socket be put in nonblocking mode by using the ioctl system call
with the FIOSNBIO request. Here is an example:
#include <sys/ioctl.h>
...
ioctl(s, FIOSNBIO, &arg);
arg is a pointer to int:
• When int equals 0, the socket is changed to blocking mode.
• When int equals 1, the socket is changed to nonblocking mode.
If a socket is in nonblocking mode, the following calls are affected:
accept
connect
recv
send
The O_NDELAY flag for fcntl(2) is also supported. If you use this flag
and there are no data available to be received on a recv, recvfrom ,
recvmsg, or read call, the call returns immediately with the value of 0.
If you use the O_NONBLOCK flag, the call returns immediately with the
value of -1 and the EAGAIN error. This is the same as returning an
end-of-file condition. This is also true for send, sendto, sendmsg, and
write if there is not enough buffer space to complete the send.
NOTE The O_NDELAY and O_NONBLOCK flags have precedence over the
FIOSNBIO flag. Setting both the O_NDELAY and O_NONBLOCK flags
is not allowed.
Chapter 3
If no connection requests are present, accept returns
immediately with the EWOULDBLOCK error.
If the connection cannot be completed immediately,
connect returns with the EINPROGRESS error.
If no data are available to be received, recv returns
the value –1 and the EWOULDBLOCK error. This is
also true for read.
If there is no available buffer space for the data to be
transmitted, send returns the value -1 and the
EWOULDBLOCK error. This is also true for write.
Advanced Topics for Stream Sockets
Nonblocking I/O
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