Telnet Client
This example connects to a Telnet server using an Ethernet shield. Messages from the server are printed out via the serial port. Messages can be sent to the remote server serially as well. The Serial monitor works well for this purpose.
Hardware Required
- Arduino or Genuino Board
- Arduino Ethernet Shield
Software Required
- A telnet server
- Alternatively, Processing has a ChatServer example that works well for this purpose
Circuit
The Ethernet shield allows you to connect a WIZNet Ethernet controller to the Arduino or Genuino boards via the SPI bus. It uses the ICSP header pins and pin 10 as chip select for the SPI connection to the Ethernet controller chip. Later models of the Ethernet shield also have an SD Card on board. Digital pin 4 is used to control the slave select pin on the SD card.
The shield should be connected to a network with an Ethernet cable. You will need to change the network settings in the program to correspond to your network.
Image developed using Fritzing. For more circuit examples, see the Fritzing project page
In the above image, the Arduino or Genuino board would be stacked below the Ethernet shield.
Code
/*
Telnet client
This sketch connects to a a telnet server (http://www.google.com)
using an Arduino Wiznet Ethernet shield. You'll need a telnet server
to test this with.
Processing's ChatServer example (part of the network library) works well,
running on port 10002. It can be found as part of the examples
in the Processing application, available at
http://processing.org/
Circuit:
* Ethernet shield attached to pins 10, 11, 12, 13
created 14 Sep 2010
modified 9 Apr 2012
by Tom Igoe
*/
#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[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
};
IPAddress ip(192, 168, 1, 177);
// Enter the IP address of the server you're connecting to:
IPAddress server(1, 1, 1, 1);
// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 23 is default for telnet;
// if you're using Processing's ChatServer, use port 10002):
EthernetClient client;
void setup() {
// You can use Ethernet.init(pin) to configure the CS pin
//Ethernet.init(10); // Most Arduino shields
//Ethernet.init(5); // MKR ETH shield
//Ethernet.init(0); // Teensy 2.0
//Ethernet.init(20); // Teensy++ 2.0
//Ethernet.init(15); // ESP8266 with Adafruit Featherwing Ethernet
//Ethernet.init(33); // ESP32 with Adafruit Featherwing Ethernet
// start the Ethernet connection:
Ethernet.begin(mac, ip);
// Open serial communications and wait for port to open:
Serial.begin(9600);
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
}
}
while (Ethernet.linkStatus() == LinkOFF) {
Serial.println("Ethernet cable is not connected.");
delay(500);
}
// give the Ethernet shield a second to initialize:
delay(1000);
Serial.println("connecting...");
// if you get a connection, report back via serial:
if (client.connect(server, 10002)) {
Serial.println("connected");
} else {
// if 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();
Serial.print(c);
}
// as long as there are bytes in the serial queue,
// read them and send them out the socket if it's open:
while (Serial.available() > 0) {
char inChar = Serial.read();
if (client.connected()) {
client.print(inChar);
}
}
// if the server's disconnected, stop the client:
if (!client.connected()) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
// do nothing:
while (true) {
delay(1);
}
}
}
Telnet client
This sketch connects to a a telnet server (http://www.google.com)
using an Arduino Wiznet Ethernet shield. You'll need a telnet server
to test this with.
Processing's ChatServer example (part of the network library) works well,
running on port 10002. It can be found as part of the examples
in the Processing application, available at
http://processing.org/
Circuit:
* Ethernet shield attached to pins 10, 11, 12, 13
created 14 Sep 2010
modified 9 Apr 2012
by Tom Igoe
*/
#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[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
};
IPAddress ip(192, 168, 1, 177);
// Enter the IP address of the server you're connecting to:
IPAddress server(1, 1, 1, 1);
// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 23 is default for telnet;
// if you're using Processing's ChatServer, use port 10002):
EthernetClient client;
void setup() {
// You can use Ethernet.init(pin) to configure the CS pin
//Ethernet.init(10); // Most Arduino shields
//Ethernet.init(5); // MKR ETH shield
//Ethernet.init(0); // Teensy 2.0
//Ethernet.init(20); // Teensy++ 2.0
//Ethernet.init(15); // ESP8266 with Adafruit Featherwing Ethernet
//Ethernet.init(33); // ESP32 with Adafruit Featherwing Ethernet
// start the Ethernet connection:
Ethernet.begin(mac, ip);
// Open serial communications and wait for port to open:
Serial.begin(9600);
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
}
}
while (Ethernet.linkStatus() == LinkOFF) {
Serial.println("Ethernet cable is not connected.");
delay(500);
}
// give the Ethernet shield a second to initialize:
delay(1000);
Serial.println("connecting...");
// if you get a connection, report back via serial:
if (client.connect(server, 10002)) {
Serial.println("connected");
} else {
// if 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();
Serial.print(c);
}
// as long as there are bytes in the serial queue,
// read them and send them out the socket if it's open:
while (Serial.available() > 0) {
char inChar = Serial.read();
if (client.connected()) {
client.print(inChar);
}
}
// if the server's disconnected, stop the client:
if (!client.connected()) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
// do nothing:
while (true) {
delay(1);
}
}
}
See also
- Arduino Ethernet Shield – Product description.
- Getting started with the Ethernet Shield – Get everything set up in minutes.
- Ethernet library – Your reference for the Ethernet Library.
- ChatServer - A simple server that distributes any incoming messages to all connected clients.
- WebClient – Query the web and get the answer through the serial monitor
- WebClientRepeating - How to make repeated HTTP requests using the Ethernet shield.
- WebServer - A simple web server that shows the value of the analog input.
- DhcpAddressPrinter – Get a DHCP address and print it on serial monitor.
- DhcpChatServer – Connect to a Telnet server and print on serial monitor all the received messages; uses DHCP.
- BarometricPressureWebServer – Post data read from a pressure sensor using SPI.
- UDPSendReceiveString - Send and receive text strings via the UDP protocol (Universal Datagram Packet).
- UdpNtpClient - query a Network Time Protocol (NTP) server and get the information through serial monitor.
Last revision 2018/09/07 by SM
