Raspberry Pi C-Server Sensor Application with websocket
Raspberry Pi C-Server Sensor Application with websocket
Getting pressure and temperature measurements from the Raspberry PI Sense Hat
REM : sensor access functions ( c language) can be found at : https://github.com/davebm1/c-sense-hat
you’ll have to install :
sudo apt-get install libi2c-devAfter websocket handshaking, the RPI gets measurements with I2C bus and sends them to the client through the websocket.
httpDynServerWs_sensor.c
// CREDITS : F. Harrouet, www.enib.fr/~harrouet
//======================================================================
// REM : all static pages have to be readable only !!
//======================================================================
#include "main.h"
#include "httpServerLib.h"
#include "libWs.h"
#include "senseHat.h"
#include <time.h>
#include <sqlite3.h>
#define BUFFER_SIZE 0x1000
//======================================================================
void * dialogThread(void *arg)
{
char header[0x100];
char handshake[29];
float pressure, temperature;
int values[2];
pthread_detach(pthread_self());
char buffer[BUFFER_SIZE];
Request *req=(Request *)arg;
//---- receive and analyse HTTP request line by line ----
bool first=true;
for(;;)
{
if(recvLine(req->sock,buffer,BUFFER_SIZE)<=0)
{ break; }
printf("%s",buffer);
if(first)
{
first=false;
sscanf(buffer,"%s %s",req->requestMethod,req->requestUri);
}
else if(sscanf(buffer,"Content-Length : %s",req->contentLength))
{
printf("CONTENTLENGTH\n");
// nothing more to be done
}
else if(!strcmp(buffer,"\n")||!strcmp(buffer,"\r\n"))
{
break; // end of header
}
else if(sscanf(buffer, "Upgrade : %31s", req->upgrade)==1)
{
// nothing more to be done
}
else if(sscanf(buffer, "Sec-WebSocket-Key : %31s", req->wsKey)==1)
{
// nothing more to be done
}
}
//------------------------------------------------------------------------------------------
//---- prepare and send HTTP reply ----
sprintf(req->fileName,"./www%s",req->requestUri);
char *params=strchr(req->fileName,'?');
if(params) { *params='\0'; }
struct stat st;
int r=stat(req->fileName,&st);
if((r!=-1)&&S_ISDIR(st.st_mode))
{
strcat(req->fileName,"/index.html");
r=stat(req->fileName,&st);
}
//------------------------------------------------------------------------------------------
//---- HANDLE UPGRADE TO WEBSOCKET REQUEST ----
if(!strcmp(req->requestMethod, "GET")&& !strcmp(req->requestUri, "/")&& !strcmp(req->upgrade, "websocket"))
{
printf("upgrading to websocket\n");
//---- prepare and send reply header ----
wsHandshake(handshake, req->wsKey);
const int hLen=snprintf(header, sizeof(header),
"HTTP/1.1 101 Switching Protocols\r\n"
"Connection: Upgrade\r\n"
"Upgrade: websocket\r\n"
"Sec-WebSocket-Accept: %s\r\n"
"\r\n",
handshake);
sendAll(req->sock, header, hLen);
//---- receive some parameters from client ----
uint32_t params[3];
WsResult r=wsRecv(req->sock, params, sizeof(params));
if((r.opcode==WS_BIN)&&(r.length!=sizeof(params)))
{
fprintf(stderr, "cannot receive parameters\n");
goto threadEnd;
}
const int repeatCount=(int)ntohl(params[2]);
//---- produce and send values to client ----
for(int repeat=0; repeat<repeatCount; ++repeat)
{
senseHat_getPressureTemperature(&pressure, &temperature);
values[0] = (int)(1000.0*pressure);
values[1] = (int)(1000.0*temperature);
sleep(2);
for(int i=0; i<2; ++i) { values[i]=htonl(values[i]); }
wsSend(req->sock, values, sizeof(values), WS_BIN); //>>>>>>>>>>>>>>>>>>>> WS SEND
}
//---- signal end of websocket dialog ----
wsSend(req->sock, NULL, 0, WS_CLOSE);
//---- websocket dialog stops here ----
goto threadEnd;
}
//------------------------------------------------------------------------------------------
// IF WE HAVE TO SERVE AN EXECUTABLE SCRIPT FILE ( CGI SCRIPT ) :
// rem : CGI scripts have to be placed in www/cgi/ folder
if((access(req->fileName,R_OK|X_OK)==0) && !strncmp(req->requestUri, "/cgi",4))
{
if(strcmp(req->requestMethod,"GET")&&strcmp(req->requestMethod,"POST"))
{
r=sprintf(buffer,"HTTP/1.0 400 Bad Request\n"
"Connection: close\n"
"Content-Type: text/html\n"
"\n"
"<html><body>\n"
"<b>400 - Bad Request</b><br>\n"
"method: %s<br>\n"
"uri: %s<br>\n"
"fileName: %s<br>\n"
"</body></html>\n",
req->requestMethod,
req->requestUri,
req->fileName);
sendAll(req->sock,buffer,r);
}
else
{
// HTTP RESPONSE HEADER
r=sprintf(buffer,"HTTP/1.0 200 OK\n"
"Connection: close\n");
sendAll(req->sock,buffer,r);
pid_t child=fork(); // execvp needs a new process, otherwhise the executed process will destroy all current threads.
switch(child)
{
case -1:
{
perror("fork");
break;
}
//############ CHILD CODE ######################################
case 0:
{
setenv("REQUEST_METHOD",req->requestMethod,1); // needed for queryProperties script
setenv("REQUEST_URI",req->requestUri,1); // needed for queryProperties script
setenv("CONTENT_LENGTH",req->contentLength,1); // needed for queryProperties script
createQueryString(req->requestUri,sizeof(req->requestUri),req->queryString);
setenv("QUERY_STRING",req->queryString,1);
printf("DEBUG REQ=%s, FILENAME=%s QUERYSTRING=%s \n",req -> requestUri, req -> fileName, req -> queryString);
if(dup2(req->sock,0)==-1)
{ perror("dup2"); exit(1); }
if(dup2(req->sock,1)==-1)
{ perror("dup2"); exit(1); }
if(dup2(req->sock,2)==-1)
{ perror("dup2"); exit(1); }
close(req->sock);
char *args[2];
args[0]=req->fileName;
args[1]=(char *)0;
execvp(args[0],args);
perror("execvp");
exit(1);
}
//############ PARENT CODE #####################################
default:
{
if(waitpid(child,(int *)0,0)==-1)
{ perror("waitpid"); }
}
}
}
}
//------------------------------------------------------------------------------------------
else // STATIC HTTP FILE SERVER
{
int input=open(req->fileName,O_RDONLY);
if(input==-1)
{
r=sprintf(buffer,"HTTP/1.0 404 Not Found\n"
"Connection: close\n"
"Content-Type: text/html\n"
"\n"
"<html><body>\n"
"<b>404 - Not Found</b><br>\n"
"method: %s<br>\n"
"uri: %s<br>\n"
"fileName: %s<br>\n"
"</body></html>\n",
req->requestMethod,
req->requestUri,
req->fileName);
sendAll(req->sock,buffer,r);
}
else
{
const char *contentType="unknown/unknown";
const char *ext=strrchr(req->fileName,'.');
if(ext)
{
if(!strcmp(ext,".html")) contentType="text/html";
else if(!strcmp(ext,".png")) contentType="image/png";
else if(!strcmp(ext,".ico")) contentType="image/vnd.microsoft.icon";
}
r=sprintf(buffer,"HTTP/1.0 200 OK\n"
"Connection: close\n"
"Content-Type: %s\n"
"Content-Length: %ld\n\n",
contentType,
st.st_size);
sendAll(req->sock,buffer,r);
for(;;)
{
r=read(input,buffer,BUFFER_SIZE);
if(r<=0) break;
sendAll(req->sock,buffer,r);
}
close(input);
}
}
threadEnd:
destroyRequest(req);
return (void *)0;
}
//======================================================================
// MAIN
//======================================================================
int main(int argc, char **argv)
{
senseHat_init();
//---- avoid exiting on broken client connection (ignore SIGPIPE) ----
struct sigaction sa;
memset(&sa,0,sizeof(struct sigaction));
sa.sa_handler=SIG_IGN;
if(sigaction(SIGPIPE,&sa,(struct sigaction *)0)==-1)
{ perror("sigaction"); exit(1); }
//---- check command line arguments ----
if(argc!=2)
{ fprintf(stderr,"usage: %s http_port\n",argv[0]); exit(1); }
//---- extract local port number ----
int httpPortNumber;
if(sscanf(argv[1],"%d",&httpPortNumber)!=1)
{ fprintf(stderr,"invalid port %s\n",argv[1]); exit(1); }
//---- multithreaded TCP server launching dialogThread() ----
//---- create HTTP listen socket ----
int httpSocket=socket(PF_INET,SOCK_STREAM,0);
if(httpSocket==-1)
{ perror("socket"); exit(1); }
// ... avoiding timewait problems (optional)
int on=1;
if(setsockopt(httpSocket,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(int))==-1)
{ perror("setsockopt"); exit(1); }
// ... bound to any local address on the specified port
struct sockaddr_in myAddr;
myAddr.sin_family=AF_INET;
myAddr.sin_port=htons(httpPortNumber);
myAddr.sin_addr.s_addr=htonl(INADDR_ANY);
if(bind(httpSocket,(struct sockaddr *)&myAddr,sizeof(myAddr))==-1)
{ perror("bind"); exit(1); }
// ... listening connections
if(listen(httpSocket,10)==-1)
{ perror("listen"); exit(1); }
for(;;)
{
//---- accept new HTTP connection ----
struct sockaddr_in fromAddr;
socklen_t len=sizeof(fromAddr);
int dialogSocket=accept(httpSocket,(struct sockaddr *)&fromAddr,&len);
if(dialogSocket==-1)
{ perror("accept"); exit(1); }
printf("new HTTP connection from %s:%d\n",
inet_ntoa(fromAddr.sin_addr),ntohs(fromAddr.sin_port));
//---- start a new dialog thread ----
pthread_t th;
if(pthread_create(&th,(pthread_attr_t *)0, dialogThread,createRequest(dialogSocket)))
{ fprintf(stderr,"cannot create thread\n"); exit(1); }
}
close(httpSocket);
return 0;
}
//^^^^^^^^^^^^^^^^^^^^^^^^^^ EOF ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
www/wsAppli.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>RPI C Server Sensor App </title>
</head>
<body>
<!--=================================================================-->
<!-- DISPLAYS
<!--=================================================================-->
<script>
display_log=function(msg)
{
var logArea = 0;
if(!logArea)
{ logArea=document.getElementById("log"); }
if(msg==null)
{ logArea.textContent='';}
else { logArea.textContent+=msg+'\n'; }
};
</script>
<!--=================================================================-->
<!-- WEBSOCKET
<!--=================================================================-->
<script type="text/javascript" charset="utf-8">
hton_i32Array=function(values){
var view=new DataView(values.buffer);
for(var i=0; i<values.length; ++i)
{
view.setInt32(i*4, values[i], false);
}
};
<!----------------------------------------------------------------->
ntoh_i32Array=function(values){
var view=new DataView(values.buffer);
for(var i=0; i<values.length; ++i)
{
values[i]=view.getInt32(i*4, false);
}
};
<!----------------------------------------------------------------->
var host=window.location.hostname;
var port=window.location.port;
var ws = new WebSocket('ws://'+host+':'+port+'/');
ws.binaryType='arraybuffer';
<!----------------------------------------------------------------->
ws.onopen=function(){
display_log('CONNECT');
};
<!----------------------------------------------------------------->
ws.onclose=function(){
display_log('DISCONNECT');
};
<!----------------------------------------------------------------->
ws.onmessage=function(evt){
var values=new Int32Array(evt.data);
ntoh_i32Array(values);
var msg='received values :';
for(var i=0; i<values.length; ++i)
{
msg+=' '+values[i]/1000.0;
}
display_log(msg);
};
<!----------------------------------------------------------------->
function start() {
console.log('start...');
nbr_meas = document.getElementById("nbr_meas");
var params=new Int32Array(3);
params[0]=1000; // delayMs
params[1]=100; // modulo
params[2]=nbr_meas.value; // only this parameter is used
hton_i32Array(params);
ws.send(params);
}
</script>
<!--=================================================================-->
<!-- ONLOAD WINDOW INIT
<!--=================================================================-->
<script>
window.onload = function() {
if(!host){
host='localhost';
port=8080;
}
};
</script>
<!--=================================================================-->
<!-- HTML -->
<!--=================================================================-->
<p>[<a href="/">home</a>]</p>
<hr> <!---------------------------------------------------------------->
<h2>Getting Sensor Datas with Websocket</h2>
<strong> Number of Measurements : </strong><br/>
<input type="text" id="nbr_meas"/> <br/>
<button onclick="start()">Start</button>
<p><b>Log:</b></p>
<p></p><pre id="log"></pre><p></p>
<hr> <!---------------------------------------------------------------->
</body>
</html>
<!--=================================================================-->
Adding LED Control
GPIO CONFIG
$ nano /etc/profile.d/gpio_config.sh
#! /bin/bash
cd /sys/class/gpio/
echo 4 > export
cd gpio4
echo out > direction
echo 1 > value
cd ~for led config, have a look at : dynamic_http_server.html
www/wsAppliLed.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>RPI C Server Sensor App </title>
</head>
<body>
<!--=================================================================-->
<!-- DISPLAYS
<!--=================================================================-->
<script>
display_log=function(msg)
{
var logArea = 0;
if(!logArea)
{ logArea=document.getElementById("log"); }
if(msg==null)
{ logArea.textContent='';}
else { logArea.textContent+=msg+'\n'; }
};
</script>
<script src="gauge.js"></script>
<!--=================================================================-->
<!-- WEBSOCKET
<!--=================================================================-->
<script type="text/javascript" charset="utf-8">
hton_i32Array=function(values){
var view=new DataView(values.buffer);
for(var i=0; i<values.length; ++i)
{
view.setInt32(i*4, values[i], false);
}
};
<!----------------------------------------------------------------->
ntoh_i32Array=function(values){
var view=new DataView(values.buffer);
for(var i=0; i<values.length; ++i)
{
values[i]=view.getInt32(i*4, false);
}
};
<!----------------------------------------------------------------->
var host=window.location.hostname;
var port=window.location.port;
var ws = new WebSocket('ws://'+host+':'+port+'/');
ws.binaryType='arraybuffer';
<!----------------------------------------------------------------->
ws.onopen=function(){
display_log('CONNECT');
};
<!----------------------------------------------------------------->
ws.onclose=function(){
display_log('DISCONNECT');
};
<!----------------------------------------------------------------->
ws.onmessage=function(evt){
var values=new Int32Array(evt.data);
ntoh_i32Array(values);
var msg='received values :';
for(var i=0; i<values.length; ++i)
{
msg+=' '+values[i]/1000.0;
}
display_log(msg);
var gauge=new Gauge('gauge');
gauge.draw(values[0]/1000.0);
};
<!----------------------------------------------------------------->
function start() {
console.log('start...');
nbr_meas = document.getElementById("nbr_meas");
var params=new Int32Array(3);
params[0]=1000; // delayMs
params[1]=100; // modulo
params[2]=nbr_meas.value; // only this parameter is used
hton_i32Array(params);
ws.send(params);
}
</script>
<!--=================================================================-->
<!-- AJAX REQUEST FOR LED CONTROL
<!--=================================================================-->
<script>
function do_onclick(led, label){
var xmlhttp=new XMLHttpRequest();
// register callback : function to be called when we receive the response
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
label.innerHTML=xmlhttp.responseText;
}
}
// send request and poll for asynchronous response
xmlhttp.open("GET","cgi/ajax_gpio4.sh?gpio4="+led.checked,true);
xmlhttp.send();
}
</script>
<!--=================================================================-->
<!-- ONLOAD WINDOW INIT
<!--=================================================================-->
<script>
window.onload = function() {
var led=document.getElementById("tLed");
var label=document.getElementById("tLedLabel");
led.checked=false;
do_onclick(led, label);
if(!host){
host='localhost';
port=8080;
}
};
</script>
<!--=================================================================-->
<!-- HTML -->
<!--=================================================================-->
<p>[<a href="/">home</a>]</p>
<hr> <!---------------------------------------------------------------->
<h2>Control GPIO4 LED</h2>
<table>
<tr>
<td >
<h3>Static Part :</h3>
Control GPIO4 led <input type="checkbox" id="tLed" onclick="do_onclick(this, document.getElementById('tLedLabel'))">
</td>
<td>
<span id="tLedLabel"> GPIO4 led turned off</span>
</td>
</tr>
</table>
<hr> <!---------------------------------------------------------------->
<h2>Getting Sensor Datas with Websocket</h2>
<table>
<tr>
<td >
<strong> Number of Measurements : </strong><br/>
<input type="text" id="nbr_meas"/> <br/>
<button onclick="start()">Start</button>
</td>
<td>
<h3> Pressure Measurement </h3>
<div >
<canvas id="gauge" width="170" height="170"></canvas>
</div>
</td>
</tr>
</table>
<p><b>Log:</b></p>
<p></p><pre id="log"></pre><p></p>
<hr> <!---------------------------------------------------------------->
</body>
</html>
<!--=================================================================-->
Adding Database Management
Let’s use a lightweight database : sqlite3
# RPI TERM
$ sudo apt-get install sqlite3 libsqlite3-devCross Compiling and Debug
please have a look at : https://web.enib.fr/~kerhoas/ide/rpi-cross-development
code_ws_sensor_led_db_cross_dev.zip