Communication programming is a fertile field for ambushing bugs, because many things in communication are random and/or are not under programmer control:

• Input data are transmitted by a remote side. Receiver has no control on their content and volumes, nor on when they are sent.
• The delay between sending data and when they reach their destination, depends on network: its congestion, changes in topology, hardware changes, physical state of wires and connectors, and a myriad of other aspects.
• Some of a socket‑related stuff is random by design.

Typically it makes the bugs practically irreproducible.

The following simple recipes may help avoid some of the bugs at the first place:

1. select

   and

   pselect

   do not scale well and may crash programs. They should not be used in enterprise‑strength codes. Use instead

   poll

   ,

   ppoll

   , or

   epoll

   .
2. Bind listener sockets to proper port numbers, that usually should be in a range 61001 – 65535.
3. Use

   poll

   and similar facilities only with non‑blocking sockets. Particularly, only with non‑blocking listener sockets.
4. Set option

   SO_REUSEADDR

   for listener sockets.

The recipies usually work right out of the box, though sometimes you need to tinker with them.