we use the service programmatically with an Arduino, see how it works using
the
telnet
command:
maik> telnet time.nist.gov 13
Trying 192.43.244.18...
Connected to time.nist.gov.
Escape character is '^]'.
56965 14-11-04 20:33:03 00 0 0 867.4 UTC(NIST) *
Connection closed by foreign host.
As soon as the
telnet
command connects to the Daytime server, it sends back
the current time and date.
10
Then the service shuts down the connection
immediately.
Here’s an implementation of exactly the same behavior for an Arduino with
an Ethernet shield:
Ethernet/TimeServer/TimeServer.ino
#include <SPI.h>
Line 1
#include <Ethernet.h>
-
const unsigned int BAUD_RATE = 9600;
-
const unsigned int DAYTIME_PORT = 13;
-
5
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
-
IPAddress my_ip(192, 168, 2, 120);
-
IPAddress time_server(192, 43, 244, 18); // time.nist.gov
-
EthernetClient client;
-
10
void setup() {
-
Serial.begin(BAUD_RATE);
-
Ethernet.begin(mac, my_ip);
-
}
-
15
void loop() {
-
delay(1000);
-
Serial.print("Connecting...");
-
-
if (client.connect(time_server, DAYTIME_PORT) <= 0) {
20
Serial.println("connection failed.");
-
} else {
-
Serial.println("connected.");
-
delay(300);
-
while (client.available()) {
25
char c = client.read();
-
Serial.print(c);
-
}
-
-
10. See
http://www.nist.gov/physlab/div847/grp40/its.cfm
for a detailed description of the date string’s
format.
Chapter 10. Networking with Arduino • 174
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