Always? I just returned from fixing a problem. A system call for UDP connection wasn't working. It worked yesterday. I could, however, ping and ssh over the network interface.
I tried an earlier branch. Same problem. After that, I replaced the NIC, rebooted, and everything worked.
Sometimes it really is the hardware/library/compiler/... There was probably a lot more investigation I could have done before going to that level (as the author suggests) but in this case it was most efficient to try replacing the card early and identify/eliminate it as the problem.
I tried an earlier branch. Same problem. After that, I replaced the NIC, rebooted, and everything worked.
Sometimes it really is the hardware/library/compiler/... There was probably a lot more investigation I could have done before going to that level (as the author suggests) but in this case it was most efficient to try replacing the card early and identify/eliminate it as the problem.