0

I am trying to make a connection with the EthernetClient, but it always fails with code 0. I decided to write a small code just to test if the client ever becomes ready, and as I suspected it does not.

#include <SPI.h>
#include <Ethernet.h>

byte mac[] = {0x2A, 0x27, 0x55, 0x08, 0x1E, 0x6A};
IPAddress ip(172, 16, 48, 133);
EthernetClient client;

void setup() {
  Ethernet.init(10);
  Ethernet.begin(mac, ip);
  Serial.begin(9600);
  while (!Serial) {;}

  for (auto link = Ethernet.linkStatus(); link != LinkON; link = Ethernet.linkStatus()) {;}
  Serial.println("Link ON");

  while(!client){
    Serial.println("Client not ready");
    delay(1000);
  }

  Serial.println("Client ready!");
}

void loop() {}

If I try to run the code above, it gets stuck at the "Client not ready" loop, and I can't figure it out what I'm missing for it to work.

Obs.: I have already configured a web server with success with my shield, so I'm guessing the problem is not with it.

Improve this question
3
  • I'm not sure why you're evaluating !client. This maps to the boolean operator which tells you if it has a connected socket (github.com/arduino-libraries/Ethernet/blob/…). Since you have not called connect() on the client, this will always return false. What actual error do you have in your full sketch? Commented Jan 10, 2020 at 20:22
  • Connect returns 0. I've looked the source and found multiple points where it might return 0, so it's hard to diagnose. Commented Jan 10, 2020 at 20:25
  • @Maximilian the reference says only that it "Indicates if the specified Ethernet client is ready." Commented Jan 10, 2020 at 20:29

1 Answer 1

Reset to default
0

An EthernetClient expects to connect to a remote socket. At no point do you instruct it to connect to a socket, so it never succeeds.

At some point before checking for a connection you need to initiate that connection:

// arduino.cc is 100.24.172.113
IPAddress server(100, 24, 172, 113);
client.connect(server, 80);

The if (client) operation relies on sockindex having been assigned a valid value, and that is only ever done either by EthernetClient::connect() or by being explicitly set by EthernetServer::available().

Improve this answer
5
  • in this example this is done to check if the client is available Commented Jan 10, 2020 at 20:34
  • @LucasNoetzold That example makes no sense. Like many on the Arduino website it's complete nonsense. You should only check if (client) to confirm a connection has been established. Normally only when using it as an incoming connection to a server. Commented Jan 10, 2020 at 20:40
  • As it states in the source code: // the next function allows us to use the client returned by // EthernetServer::available() as the condition in an if-statement. Commented Jan 10, 2020 at 20:42
  • I'll have to find why connect is returning 0 then. Thanks. Commented Jan 10, 2020 at 20:54
  • 0 indicates DNS name resolve failure. github.com/arduino-libraries/Ethernet/blob/… @LucasNoetzold Commented Jan 10, 2020 at 21:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.