HP Rp3440-4 - 9000 - 0 MB RAM Programmer's Manual page 178

Programming Hints
Portability Issues
FIONREAD Return Values
For HP-UX systems, the FIONREAD ioctl request on a datagram
socket returns a number that may be larger than the number of bytes
actually readable. Previously, HP-UX systems returned the maximum
number of bytes that a subsequent recv would be able to return.
Listen's Backlog Parameter
HP-UX sets the actual size of the queue for pending connections to 3/
2*B+1, where B is the backlog value specified in the listen()
function. This may change in future releases, but it will not be smaller
than the backlog value.
Pending Connections
There is no guarantee which pending connection on a listening socket is
returned by accept. HP-UX systems return the newest pending
connection. Applications should be written such that they do not depend
upon connections being returned by accept on a first-come, first-served
basis.
Porting Issues for Other Functions and
Library Calls Typically Used by IPC
The following is a list of differences in functions and library calls to
watch out for when you port your IPC applications between HP-UX and
4.3 BSD systems.
Ioctl and Fcntl Calls
4.3 BSD terminal ioctl calls are incompatible with the HP-UX
implementation. These calls are typically used in virtual terminal
applications. The HP-UX implementation uses UNIX System V
compatible calls.
Pty Location
Look for the pty masters in /dev/ptym/ptyp? and for the pty slaves in
/dev/pty/ttyp?. An alternative location to check is /dev.
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