Basic Library

Digital I/O
Analog I/O
Advanced I/O
Time
Math
Trigonometry
Random Numbers
Bits and Bytes
Interrupts
Serial Comm.

Standard Library

Ethernet
Ethernet (Server)
Ethernet (Client)
Servo Motor
Stepping Motor
Character LCD
EEPROM
SPI
I2C (Wire)
SD Card
SD (File Operations)
Periodic Operation
Clock (RTC)
Utility

Ethernet Server

Create a server that listens for incoming connections on the specified port.

EthernetServer()

Description
Constructor to create a server.
Syntax (Example)
EthernetServer server(uint16_t port)
Parameters
The port to listen on (uint16_t)

begin

Description
Tells the server to begin listening for incoming connections.
Syntax
server.begin()
Parameters
None
Returns
None

available

Description
Gets a client that is connected to the server and has data available for reading. The connection persists when the returned client object goes out of scope.
Syntax
server.available()
Parameters
None
Returns
Returns a Client object; if no Client has data available for reading, this object will evaluate to false in an if-statement.

write

Description
Write data to all the clients connected to a server. This data is sent as a byte or series of bytes.
Syntax
server.write(val)
server.write(buf, len)
Parameters
val: A value to send as a single byte (byte or char)
buf: An array to send as a series of bytes (byte or char)
len: The length of the buffer
Returns
Byte
write() returns the number of bytes written. It is not necessary to read this.

print

Description
Print data to all the clients connected to a server. Prints numbers as a sequence of digits, each an ASCII character (e.g. the number 123 is sent as the three characters '1', '2', '3').
Syntax
server.print(data)
server.print(data, BASE)
Parameters
data: The data to print (char, byte, int, long, or string)
BASE (optional): The base in which to print numbers: BIN for binary (base 2), DEC for decimal (base 10), OCT for octal (base 8), HEX for hexadecimal (base 16)
Returns
Byte
print() will return the number of bytes written, though reading that number is optional.

println

Description
Print data, followed by a newline, to all the clients connected to a server. Prints numbers as a sequence of digits, each an ASCII character (e.g. the number 123 is sent as the three characters '1', '2', '3').
Syntax
server.println()
server.println(data)
server.println(data, BASE)
Parameters
data (optional): The data to print (char, byte, int, long, or string) BASE (optional): The base in which to print numbers: BIN for binary (base 2), DEC for decimal (base 10), OCT for octal (base 8), HEX for hexadecimal (base 16)
Returns
Byte
println() will return the number of bytes written, though reading that number is optional.

Sample Program

Sample for Ethernet server library. The server returns to a client the result of analogRead A0-A5.


#include <Arduino.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
};
 
// Initialize the Ethernet server library
// with the IP address and port you want to use
// (port 80 is default for HTTP):
EthernetServer server(80);
  
void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial.available()) ; // wait to press key
 
  // start the Ethernet connection and the server:
  Ethernet.begin(mac);
  server.begin();
  Serial.print("server is at ");
  Serial.println(Ethernet.localIP());
}
 
void loop() {
  // listen for incoming clients
  EthernetClient client = server.available();
  if (client) {
    Serial.println("new client");
    // an http request ends with a blank line
    boolean currentLineIsBlank = true;
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();
        Serial.write(c);
        // if you've gotten to the end of the line (received a newline
        // character) and the line is blank, the http request has ended,
        // so you can send a reply
        if (c == '\n' && currentLineIsBlank) {
          // send a standard http response header
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println("Connection: close");  // the connection will be closed after completion of the response
          client.println("Refresh: 5");  // refresh the page automatically every 5 sec
          client.println();
          client.println("<!DOCTYPE HTML>");
          client.println("<html>");
          // output the value of each analog input pin
          for (int analogChannel = 0; analogChannel < 6; analogChannel++) {
            int sensorReading = analogRead(analogChannel);
            client.print("analog input ");
            client.print(analogChannel);
            client.print(" is ");
            client.print(sensorReading);
            client.println("<br/ >");
          }
          client.println("</html>");
          break;
        }
        if (c == '\n') {
          // you're starting a new line
          currentLineIsBlank = true;
        }
        else if (c != '\r') {
          // you've gotten a character on the current line
          currentLineIsBlank = false;
        }
      }
    }
    // give the web browser time to receive the data
    delay(1);
    // close the connection:
    client.stop();
    Serial.println("client disconnected");
  }
}