How to detect unplugged LAN cable ?

Question

Hello there… i am having problem with detecting unplugged LAN cable. i read that i must turn on the keep alive timer, so if the remote client/server doesnt reply when keep alive timer send 1 byte data, W5500 will generate timeout interrupt, and then i can close the socket. And then i found something weird. I did 3 type of testing. the result is: TESTING 1 set socket 0 to TCP server socket 0 OPEN set keep alive timer to 1 (5 secs) socket 0 LISTEN remote TCP Client connecting to W5500 connected, socket status become 0x17 TCP client send some data, received normally by W5500 and then i unplugged the LAN cable after some time, socket TIMEOUT occurs (as expected) socket 0 closed, back to point 2 TESTING 2 set socket 0 to TCP server socket 0 OPEN set keep alive timer to 1 (5 secs) socket 0 LISTEN remote TCP Client connecting to W5500 connected, socket status become 0x17 W5500 send some data, received normally by remote TCP client and then i unplugged the LAN cable after some time, socket TIMEOUT occurs (as expected) socket 0 closed, back to point 2 TESTING 3 set socket 0 to TCP server socket 0 OPEN set keep alive timer to 1 (5 secs) socket 0 LISTEN remote TCP Client connecting to W5500 connected, socket status become 0x17 do nothing and then i unplugged the LAN cable i waited, but no timeout at all. i am confused about TESTING 3. do i have to send/receive data first, so the timeout will occur? or there is another way to detect unplugged cable?

Yaumen · Answer

Hi. I determine a link link this: linked: (getPHYCFGR() & PHYCFGR_LNK_ON) unlinked: !(getPHYCFGR() & PHYCFGR_LNK_ON)

kejuqeju · Answer

Hello Yaumen, thank you for your advice. I implemented it, and it worked OK.