jim hamblen / Mbed OS 4180_TCPSocket_Example

Alternative TCPSocket example using an HTTP GET to read a short "helloworld" text web page using a different server

Fork of ARMs demo HTTP socket demo. ARM's server was redirected and the demo was no longer working. An alternative server was setup and the code was modified to display the web page text in addition to just "200 OK". Only works for a very short web page - buffer only 400 characters but RAM is running out on the LPC1768 in the demo! Data read from the web page is read and parsed to control the mbed's 4 LEDs for a basic IoT demo.

main.cpp@6:9cf6630fa25d, 2021-02-17 (annotated)

Committer:
4180_1
Date:
Wed Feb 17 18:55:05 2021 +0000
Revision:
6:9cf6630fa25d
Parent:
5:66c4a71d22e9 
ver 1.2 Added Basic IoT demo controlling LEDs from web page data

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mab5449 0:6b383744246e 1 #include "mbed.h"
mab5449 0:6b383744246e 2 #include "EthernetInterface.h"
4180_1 6:9cf6630fa25d 3 BusOut leds(LED1,LED2,LED3,LED4); //LEDs are controlled by web page text data
mab5449 0:6b383744246e 4 // Network interface
mab5449 0:6b383744246e 5 EthernetInterface net;
mab5449 0:6b383744246e 6
mab5449 0:6b383744246e 7 // Socket demo
4180_1 6:9cf6630fa25d 8 int main()
4180_1 6:9cf6630fa25d 9 {
4180_1 5:66c4a71d22e9 10 // Show MAC in case it is needed to enable DHCP on a secure network
4180_1 5:66c4a71d22e9 11 char mac[6];
4180_1 5:66c4a71d22e9 12 mbed_mac_address(mac);
4180_1 6:9cf6630fa25d 13 printf("\r\rmbed's MAC address is %02x:%02x:%02x:%02x:%02x:%02x\n\r", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
mab5449 0:6b383744246e 14 // Bring up the ethernet interface
4180_1 5:66c4a71d22e9 15 printf("Waiting for IP address from DHCP Server\n\r");
4180_1 5:66c4a71d22e9 16 wait(1.0);
4180_1 5:66c4a71d22e9 17 net.connect();
4180_1 3:576f312d2601 18 printf("\n\rEthernet socket example\n\r");
mab5449 0:6b383744246e 19
mab5449 0:6b383744246e 20 // Show the network address
mab5449 0:6b383744246e 21 const char *ip = net.get_ip_address();
4180_1 5:66c4a71d22e9 22 printf("IP address is: %s\n\r", ip ? ip : "Timeout - No IP obtained");
mab5449 0:6b383744246e 23
mab5449 0:6b383744246e 24 // Open a socket on the network interface, and create a TCP connection to mbed.org
mab5449 0:6b383744246e 25 TCPSocket socket;
mab5449 0:6b383744246e 26 socket.open(&net);
4180_1 3:576f312d2601 27 socket.connect("hamblen.ece.gatech.edu", 80);
mab5449 0:6b383744246e 28
mab5449 0:6b383744246e 29 // Send a simple http request
4180_1 3:576f312d2601 30 char sbuffer[] = "GET /hello.txt HTTP/1.1\r\nHost: hamblen.ece.gatech.edu\r\n\r\n";
mab5449 0:6b383744246e 31 int scount = socket.send(sbuffer, sizeof sbuffer);
4180_1 3:576f312d2601 32 //print out packet
4180_1 4:d3627ca18f87 33 printf("sent %d [%.*s]\n\r", scount, strstr(sbuffer, "\r\n")-sbuffer, sbuffer);
mab5449 0:6b383744246e 34
4180_1 3:576f312d2601 35 // Recieve a simple http response and print out the response line and text
4180_1 3:576f312d2601 36 char rbuffer[400]; //enough for a very short text page - almost out of RAM!
mab5449 0:6b383744246e 37 int rcount = socket.recv(rbuffer, sizeof rbuffer);
4180_1 5:66c4a71d22e9 38 rbuffer[rcount] = 0; //terminate to print as a C string;
4180_1 6:9cf6630fa25d 39 //Print packet read from HTTP web page server
4180_1 3:576f312d2601 40 printf("recv %d [%.*s]\n\r", rcount, strstr(rbuffer, "\r\n"), rbuffer);
mab5449 0:6b383744246e 41
mab5449 0:6b383744246e 42 // Close the socket to return its memory and bring down the network interface
mab5449 0:6b383744246e 43 socket.close();
mab5449 0:6b383744246e 44
4180_1 6:9cf6630fa25d 45 // Basic IoT demo controlling mbeds 4 LEDs from Internet web page's ASCII text data
4180_1 6:9cf6630fa25d 46 // Web page demo contains a line "Data:0101"
4180_1 6:9cf6630fa25d 47 char *data;
4180_1 6:9cf6630fa25d 48 data = strstr(rbuffer,"Data:"); //Find Data: line on web page with '0's or '1's
4180_1 6:9cf6630fa25d 49 data = data + 5; //Skip to data
4180_1 6:9cf6630fa25d 50 for (int i=0; i<=3; i++) //Parse 4 web page characters to control LEDs
4180_1 6:9cf6630fa25d 51 leds[i] = data[i] - '0'; //convert ASCII '0' or '1's to binary to control 4 leds
4180_1 6:9cf6630fa25d 52 //Another device could change the web page contents to control LEDs from anywhere
4180_1 6:9cf6630fa25d 53
mab5449 0:6b383744246e 54 // Bring down the ethernet interface
mab5449 0:6b383744246e 55 net.disconnect();
4180_1 5:66c4a71d22e9 56 printf("Done\n\r");
mab5449 0:6b383744246e 57 }