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Topic: UNO + Ethernet Shield cannot connect to anything (Read 1 time) previous topic - next topic


Hello everyone,
My first time posting. Been playing with the arduino uno for a while now and this week decided to get the arduino ethernet shield. Considering how relatively easy learning the arduino was, this ethernet shield is driving me crazy.
I have been trying the webserver and webclient example sketches, and neither one lets me connect.
I had changed the MAC address to what came with the shield, IP address I assigned to it on my network, and have tried numerous server addresses ( both external internet webpages and local webpages running on my local webserver ). When I go into my router, I can see the arduino connected to my router. I can even ping it from the windows command prompt. But it does fail the ping about 25% of the time. I have tried different network cables, played with the baud rate, and also specifically opened a door for it in my firewall. Only thing I noticed was that the pinging of the arduino seemed to be more successful with a shorter network cable ( I found that odd ).
I have searched these forums and googled for days now without much success.

Does anyone have any suggestions or ideas? I would appreciate any help. Thanks!

This is all that is displayed in my serial monitor with the corresponding code beneath:
connection failed


Code: [Select]
 Web client

This sketch connects to a website (http://www.google.com)
using an Arduino Wiznet Ethernet shield.

* Ethernet shield attached to pins 10, 11, 12, 13

created 18 Dec 2009
by David A. Mellis


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

// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = {  0x90, 0xA2, 0xDA, 0x00, 0x9F, 0xDC };
byte ip[] = { 192,168,1,177 };
byte server[] = { 208,104,2,86 }; // Google
//byte server[] = {192,168,1,3};

// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
Client client(server, 80);

void setup() {
 // start the Ethernet connection:
 Ethernet.begin(mac, ip);
 // start the serial library:
 // give the Ethernet shield a second to initialize:

 // if you get a connection, report back via serial:
 if (client.connect()) {
   // Make a HTTP request:
   client.println("GET /~shb/arduino.txt HTTP/1.0");
 //  client.println("GET /index1.html HTTP/1.0");
 else {
   // kf you didn't get a connection to the server:
   Serial.println("connection failed");

void loop()
 // if there are incoming bytes available
 // from the server, read them and print them:
 if (client.available()) {
   char c = client.read();

 // if the server's disconnected, stop the client:
 if (!client.connected()) {

   // do nothing forevermore:


Only thing I noticed was that the pinging of the arduino seemed to be more successful with a shorter network cable ( I found that odd ).

That almost sounds like a power supply problem. How are you powering the boards? Regulated 5 volt, usb, or power plug?
Are you certain the voltage at the 5v pin is 5 volts?


I am powering the arduino with a USB cable. I never checked the voltage or tried powering it any other way.
Thanks for the suggestion, I will try it out.


I checked the voltage and it looks good. I borrowed a friends router to make sure it wasn't that, and I get the same problem with a completely different router.
Is there anything else I can try to debug the connection attempt? Or to track down where it is failing? Is there anything I can test to make sure the ethernet shield isn't just a bad shield?


So I tried a few more things. I pulled a mega2560 out of another project and pulled the ethernet shield off the uno and put it on. I still get the same results. Somewhere along the lines I did something that resolved the inconsistent pinging issue. It now pings perfectly fine 100% of the time. But unfortunately I still cannot get a connection to the internet from the ethernet shield.
Other than the sketch, is there any configuration I need to do to get the arduino/ethernet shield to connect to the internet?
I am almost thinking of buying another ethernet shield to see if its just not a bad shield (but I really prefer not too). Is there any way to test the shield to see if it's bad?
I appreciate any suggestions.


Is there a local server you can use for a test? Does your router display a webpage if you enter its ip in a web browser?
...or any server on that net. I see you tried Is that a web server? Does it display a web page if you enter that ip in a web browser?


Yeah, I've been using a local web server ( for my tests (as well as external web pages), both having the same failures. I can connect to my internal web server from a web browser internally or externally just fine.
Yes, when I enter the router's address into a web browser, I can connect to the router. In the router itself I can see all my connected devices, including the ethernet shield connected to the router.

If you have any further suggestions, I am willing to try anything.


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