why it can not access the destination Host when the network cable is disconnected for a moment and later this connected again?
//---------------------------------------------------------------------------- // Thread 'Server': BSD Server socket process //---------------------------------------------------------------------------- static void Server (void const *arg) { SOCKADDR_IN addr; int sock, sd, res; int type = (int)arg; char dbuf[4];
while (1) { sock = socket (AF_INET, type, 0); addr.sin_port = htons(PORT_NUM); addr.sin_family = PF_INET; addr.sin_addr.s_addr = INADDR_ANY; bind (sock, (SOCKADDR *)&addr, sizeof(addr)); if (type == SOCK_STREAM) { listen (sock, 1); sd = accept (sock, NULL, NULL); closesocket (sock); sock = sd; } while (1) { res = recv (sock, dbuf, sizeof (dbuf), 0); if (res <= 0) { break; } if (dbuf[0] == BLINKLED) { LED_Out (dbuf[1]); } } closesocket (sock); } }
Hello,
If you disconnect and reconnect a cable when using a fixed IP address, you may be falling victim to 'TIME-WAIT '
en.wikipedia.org/.../File:Tcp_state_diagram_fixed_new.svg
in your case he server may be
"... represents waiting for enough time to pass to be sure the remote TCP received the acknowledgment of its connection termination request. [According to RFC 793 a connection can stay in TIME-WAIT for a maximum of four minutes known as a MSL (maximum segment lifetime)."
so if you are always sending to the same destination IP address and port, and if you are using the same fixed IP address, the server may think these are just lost packets floating around and garbage collect them (and not respond to them). After the MSL expires (I believe 4ish minutes on windows) you would be able to trasmit again.
I believe this idea is in RFC 763 (1981) pg 27.