Server not rejecting client connections not destined for the server port

SheetLightning commented 4 years ago

I have started a server with for example in the definitions:

EthernetServer ethServer(8080);

In void setup():

ethServer.begin();

In the loop I am accepting data from a connected client:

      EthernetClient ethClient = ethServer.available();
      if (ethClient){
        if (ethClientConnected){
          while (ethClient.available()) {
            // Read the bytes incoming from the client:
            char chr = ethClient.read();
            // Echo the bytes to serial
            Serial.write(chr);
          }
        }
      }else{
        if (ethClientConnected){
          ethClient.stop();
          ethClientConnected = false;
        }
      }
  }

However, I found that it is also possible to connect with any other TCP port. The client will not accept or receive data on that port and will eventually time out, but the client (PuTTY) is establishing a connection rather than being immediately rejected as might be expected. Tried with both RAW and Telnet options.

What is more, if you change port with:

ethServer = EthernetServer(port);

The existing port does not disconnect as might be expected. It no longer processes data, but remains a connected 'zombie' until the client is shut down.

Finally, why no server.stop() method? Should it not be possible to not only start, but also to stop a server (as indeed one can with WiFi)?

Rotzbua commented 4 years ago

Hint: Do not forget to call maintain() in loop.

JAndrassy commented 4 years ago

Hint: Do not forget to call maintain() in loop.

why? it only handles the DHCP lease

JAndrassy commented 4 years ago

I can't replicate it. I get "Connection refused".

duro@nuc ~ $ telnet 192.168.1.6 2323
Trying 192.168.1.6...
Connected to 192.168.1.6.
Escape character is '^]'.

16:27:31;11019;R100;308;-3;98;-18;279;787;372;636;236;387;
16:27:35;11019;R100;329;37;98;-16;286;759;346;625;236;366;
C
Connection closed by foreign host.
duro@nuc ~ $ telnet 192.168.1.6 23
Trying 192.168.1.6...
telnet: Unable to connect to remote host: Connection refused

EDIT: I tested the port change too. The old port was refused after a short time.

duro@nuc ~ $ telnet 192.168.1.177 8080
Trying 192.168.1.177...
Connected to 192.168.1.177.
Escape character is '^]'.

HTTP/1.1 200 OK
Content-Type: text/html
Connection: close

<!DOCTYPE HTML>
<html>
analog input 0 is 813<br />
</html>
Connection closed by foreign host.
duro@nuc ~ $ telnet 192.168.1.177 8080
Trying 192.168.1.177...
Connected to 192.168.1.177.
Escape character is '^]'.

telnet> quit
Connection closed.
duro@nuc ~ $ telnet 192.168.1.177 8080
Trying 192.168.1.177...
telnet: Unable to connect to remote host: Connection refused
duro@nuc ~ $ telnet 192.168.1.177 80
Trying 192.168.1.177...
Connected to 192.168.1.177.
Escape character is '^]'.

HTTP/1.1 200 OK
Content-Type: text/html
Connection: close

<!DOCTYPE HTML>
<html>
analog input 0 is 842<br />
</html>
Connection closed by foreign host.

JAndrassy commented 4 years ago

the test in my previous comment was with W5500. with W5100 I could replicate the issue.

SheetLightning commented 4 years ago

Thanks for your tests with the W5500 vs the W5100. The results of your test with the W5500 is how I would expect it to behave, but as you have now confirmed, the W5100 behaves differently. Remains to be determined how the W5200 behaves.

Regarding Ethernet.maintain(), just to confirm that I am working with static IP addresses so there should be no need to maintain a DHCP lease.

Rotzbua commented 4 years ago

Does the problem also occur with old library version v1.1.2? Maybe something went wrong in v2.

SheetLightning commented 4 years ago

It was worth a try, but just tested with 1.1.2 and with 1.0.5 and unfortunately yes, it does occur with both of these earlier versions as well.

SheetLightning commented 4 years ago

I raised a case with the people over at WizNet and having investigated the problem, they seem to think this is related to the Arduino library:

I think we or you need to check the Ethernet library in Arduino IDE. Because this issue didn’t occur in the io-library code we provide,it is for embedded user.

I do hope this can be fixed in the library?

https://forum.wiznet.io/t/topic/7470/3

arduino-libraries / Ethernet

Server not rejecting client connections not destined for the server port #133