DHCP Chat Server

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.

This version attempts to get an IP address using DHCP. An IP address can be assigned via DHCP when Ethernet.begin(mac) is called. Be careful, when using the DHCP extensions, sketch size increases significantly.

Step 1: What You Need?

1 x Arduino Board ( Arduino UNO used in this tutorial) 
1 x Arduino Ethernet Shield

Software Required

- A telnet server 

- Alternatively, Processing has a ChatServer example that works well for this purpose

Don't have components? Don't worry. Just click the component's name. 

Step 2: Build Your Circuit.

The Ethernet shield allows you to connect a WizNet Ethernet controller to the Arduino boards via the SPI bus. It uses pins 10, 11, 12, and 13 for the SPI connection to the WizNet. 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.

In the above image, the Arduino or Genuino board would be stacked below the Ethernet shield.

Step 3: Upload The Code.

1. Select the Arduino board type: Select Tools >> Board >> Select your correct Arduino board used.

2. Find the port number by accessing device manager on Windows. See the section Port (COM&LPT) and look for an open port named "Arduino Uno (COMxx)". If you are using a different board, you will find a name accordingly. What matters is the xx in COMxx part. In my case, it's COM3. So my port number is 3.

Select the right port: Tools >> Port >> Select the port number.

3. You can find this code in the example of Arduino IDE.

Select File >> Examples >> Ethernet >>DhcpChatServer

Click press the "upload" button (see the button with right arrow mark).

/*
DHCP Chat Server A simple server that distributes any incoming messages to all
connected clients. 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. THis version attempts to get an IP address using DHCP Circuit:
* Ethernet shield attached to pins 10, 11, 12, 13 created 21 May 2011
modified 9 Apr 2012
by Tom Igoe
modified 02 Sept 2015
by Arturo Guadalupi
Based on ChatServer example 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.
// gateway and subnet are optional:
byte mac[] = {
0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x02
};
IPAddress ip(192, 168, 1, 177);
IPAddress myDns(192,168,1, 1);
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 0, 0); // telnet defaults to port 23
EthernetServer server(23);
boolean gotAMessage = false; // whether or not you got a message from the client yet void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
// this check is only needed on the Leonardo:
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
} // start the Ethernet connection:
Serial.println("Trying to get an IP address using DHCP");
if (Ethernet.begin(mac) == 0) {
Serial.println("Failed to configure Ethernet using DHCP");
// initialize the Ethernet device not using DHCP:
Ethernet.begin(mac, ip, myDns, gateway, subnet);
}
// print your local IP address:
Serial.print("My IP address: ");
ip = Ethernet.localIP();
for (byte thisByte = 0; thisByte < 4; thisByte++) {
// print the value of each byte of the IP address:
Serial.print(ip[thisByte], DEC);
Serial.print(".");
}
Serial.println();
// start listening for clients
server.begin(); } void loop() {
// wait for a new client:
EthernetClient client = server.available(); // when the client sends the first byte, say hello:
if (client) {
if (!gotAMessage) {
Serial.println("We have a new client");
client.println("Hello, client!");
gotAMessage = true;
} // read the bytes incoming from the client:
char thisChar = client.read();
// echo the bytes back to the client:
server.write(thisChar);
// echo the bytes to the server as well:
Serial.print(thisChar);
Ethernet.maintain();
}
}

Download:

Arduino IDE

Sources:https://www.arduino.cc/en/Tutorial/DhcpChatServer   

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My Robot Education Sdn. Bhd. (Robotedu.my) was founded in 2015 as the first robotics education centre in Malaysia to provide Arduino-based robotics courses for youths. Our vision is to be able to provide robotics education to every youth in Malaysia.