W5500 FIN packet

Question

Hello all, can i transfer data after receiving FIN packet(SOCKET_CLOSE_WAIT status, 0x1C)? as i think w5500 will automatically send FIN-ACK packet after receiving FIN thanks

Eugeny · Answer

Technologically you can, but will other side be still listening? Party sending FIN packet informs another party that former does not have anything more to say. Thus if your application sees FIN state, it means that another device is done sending its data, and you must not expect anything from there. But it does not mean you can not send anything in the direction of that device. If that device is still listening, it will be acknowledging packets you send, but if that device is finished completely and closed all sockets and pursged its buffers, you will receive RST packet in response and W5500 will close the socket.

Giorgi Kurtanidze · Answer

i wrote w5500 driver, TCP client and server, it works perfectly, but sometimes connection process took too long time, debugging log shows that SYN packet is transmitted (0x15 status) , what might be ?

Giorgi Kurtanidze · Answer

yes , but after disconnecting, here is log, frst is a socket status, and second is command

Giorgi Kurtanidze · Answer

at first i am closing port(uninit all) than opening, and at last connecting , but sometimes timeout is generated by w5500

Eugeny · Answer

You must use different source ports if connecting to the same server with the same destination port # in less than several minutes. Routers and target node may cache source port#/destination IP address/destination port# information and treat them as continuation as previous connection and do not respond with SYN and rather respond with RST.

Giorgi Kurtanidze · Answer

i am using source ports according IANA, from 49152 and above TCP server destination port is 9999

Giorgi Kurtanidze · Answer

thanks, can i use random ports from 49152 - 65535? as i guessed , i must use different port for each connection?

Giorgi Kurtanidze · Answer

you meant RST packet?

Giorgi Kurtanidze · Answer

for example , after resetting my device(w5500) i set src port 49152 , i received data from server, and server sent me FYN packet, i disconnect current connection. for new connection to the same server with same port and ip i must use 49153 or somethin, not 49152 , i will try that

Giorgi Kurtanidze · Answer

Giorgi_Kurtanidze: 49152 unfortunately i have the same issue ((

Giorgi Kurtanidze · Answer

i also think so, that server is responded and packet is not delivered to chip, but still i have not any idea how to solve, i can install Wireshark

Eugeny · Answer

Sometimes it happens here to me if there’re problems on the network. But route from my client to the server is relatively long, not sure about situation in your case. If it is short and under your control then you can perform exhaustive troubleshooting and get an idea what is wrong and how to fix or mitigate it.

Giorgi Kurtanidze · Answer

i tasted with google server, and it works , but with my server sometimes have connection issue, strange

Giorgi Kurtanidze · Answer

tomorrow i will install Wireshark, :)) thanks again ))

Giorgi Kurtanidze · Answer

Hello, with remote server SYN packet is received by server, but in my side SYN-ACK packet is not recevied, in local network all is working perfectly, i think that is network issue

Giorgi Kurtanidze · Answer

Hello all, how can i make multiple connection on same port in server mode, if all sockets have the same port number, client request will get all sockets

Giorgi Kurtanidze · Answer

if it is so, i can check connection state and determine connected socket ))

Eugeny · Answer

Of course, first request went with getting web page contents, another went with favicon.ico which is automatically requested by the Chrome (or other browser).

Giorgi Kurtanidze · Answer

thank u very much , i modified a little bit my code an it is working with 8 socket