T41 noob here (but have used the T40).
I'm trying to get two T41's to talk to each other over Ethernet using the NativeEthernet + FNET ZIP libs from Github. Both T41s are equipped with the PJRC magjack kit.

I've started at square 1 with the Advanced Chat Server Example, trying to get just *one* T41 talking to a Telnet window on my Win10 box.

I only changed the IP addresses to fit my network in the example code, but it's pasted below for the sake of completion.

I can connect to the T41 via Telnet.
T41 confirms the client connection
"Hello, client number: 0" shows up in my Windows Telnet session

....but that's it. Any further input into my telnet box results in *nothing* on the other (T41) end.

If I close the Telnet window, the T41 reports "disconnect client #0"

I'm guessing this is just some stupid mistake/misunderstanding on my part. Any know what it is?

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 Advanced Chat Server

 A more advanced server that distributes any incoming messages
 to all connected clients but the client the message comes from.
 To use, telnet to your device's IP address and type.
 You can see the client's input in the serial monitor as well.
 Using an Arduino Wiznet Ethernet shield.

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

 created 18 Dec 2009
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe
 redesigned to make use of operator== 25 Nov 2013
 by Norbert Truchsess


#include <SPI.h>
#include <NativeEthernet.h>

// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network.
// gateway and subnet are optional:
byte mac[] = {
  0x04, 0xE9, 0xE5, 0x0D, 0x62, 0x08
IPAddress ip(192, 168, 86, 99);
IPAddress myDns(192, 168, 86, 1);
IPAddress gateway(192, 168, 86, 1);
IPAddress subnet(255, 255, 0, 0);

// telnet defaults to port 23
EthernetServer server(23);

EthernetClient clients[8];

void setup() {
  // initialize the Ethernet device
  Ethernet.begin(mac, ip, myDns, gateway, subnet);

  // Open serial communications and wait for port to open:
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only

  // Check for Ethernet hardware present
  if (Ethernet.hardwareStatus() == EthernetNoHardware) {
    Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware. :(");
    while (true) {
      delay(1); // do nothing, no point running without Ethernet hardware
  if (Ethernet.linkStatus() == LinkOFF) {
    Serial.println("Ethernet cable is not connected.");

  // start listening for clients

  Serial.print("Chat server address:");

void loop() {
  // check for any new client connecting, and say hello (before any incoming data)
  EthernetClient newClient = server.accept();
  if (newClient) {
    for (byte i=0; i < 8; i++) {
      if (!clients[i]) {
        Serial.print("We have a new client #");
        newClient.print("Hello, client number: ");
        // Once we "accept", the client is no longer tracked by EthernetServer
        // so we must store it into our list of clients
        clients[i] = newClient;

  // check for incoming data from all clients
  for (byte i=0; i < 8; i++) {
    if (clients[i] && clients[i].available() > 0) {
      // read bytes from a client
      byte buffer[80];
      int count = clients[i].read(buffer, 80);
      // write the bytes to all other connected clients
      for (byte j=0; j < 8; j++) {
        if (j != i && clients[j].connected()) {
          clients[j].write(buffer, count);

  // stop any clients which disconnect
  for (byte i=0; i < 8; i++) {
    if (clients[i] && !clients[i].connected()) {
      Serial.print("disconnect client #");
Thanks all. This looks like a great library and hardware. Looking forward to getting past Step 1.