Now we see how to handle the webhooks on a Raspberry Pi using C.
This example can also be easily modified to work on Windows using Cygwin, the file download also includes the Windows version.
In order to receive data from the PHP file we need to listen on a socket. This example shows how to get the incoming data from the socket and process the parameters that are passed.
Once the parameters are found the Raspberry Pi then either performs an action or sends back some data to the socket.
First we declare an enum for the parameters so that we don't have to remember the parameter positions.
enum PARAMS
{
COM,
VAL,
KEY,
SUB,
DEV
};
It's a good idea to listen for data on a new thread, otherwise the rest of the program will hang while listening for an incoming connection.
Here we start the listening ServerThread.
void StartServer()
{
pthread_t tl;
pthread_create(&tl,NULL,ServerThread,NULL);
}
In the server thread we set up the server and start listening for an incoming connection:
void * ServerThread()
{
struct addrinfo hints, *server;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE || SOCK_NONBLOCK;
getaddrinfo(NULL, "8090", &hints, &server);
int sockfd = socket(server->ai_family,server->ai_socktype, server->ai_protocol);
bind(sockfd, server->ai_addr, server->ai_addrlen);
listen(sockfd, 100);
struct sockaddr_storage client_addr;
socklen_t addr_size = sizeof client_addr;
char buffer[2048];
while(1)
{
printf("Waiting for connection\n");
client_fd = accept(sockfd,(struct sockaddr *) &client_addr, &addr_size);
printf("Client connected\n");
struct timeval tv;
tv.tv_sec = 11;
tv.tv_usec = 0;
//timeout in seconds until the read function gives up
setsockopt(client_fd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof tv);
//allow the address to be reused so that we can reconnect straight away
setsockopt(client_fd, SOL_SOCKET, SO_REUSEADDR, &(int){ 1 }, sizeof(int));
Once the client is connected we read the data that was sent.
if (client_fd > 0)
{
printf("Data received from client\n");
while(read(client_fd, buffer, 2048) > 0)
{
printf("Received: %s\n", buffer);
The incoming parameters are split at the commas and stored in an array.
char *p_buf = buffer;
char Arguments[5][128];
char *token;
int count = 0;
while ((token = strsep(&p_buf, ",")) != NULL && count<5)
{
strcpy(Arguments[count],token);
printf("Data at argument %d: %s\n",count,Arguments[count]);
count++;
}
The commands implemented are 'show' and 'get'.
The 'show' command takes a value parameter of 1, 2 or 3 and when executed displays a message on screen.
The 'get' command can be used with the key parameter of 'value1', 'value2' or 'value3' and when executed returns a value to the client.
char returnBuffer[10];
bool found=false;
//Check the command
if(strncmp("show",Arguments[COM],4) == 0)
{
//perform a command
printf("Command received\n");
//Get the value parameter
char x = Arguments[VAL][0];
switch(x)
{
case '1':
printf("1 Selected\n");
found=true;
strcpy(returnBuffer,"OK\n");
break;
case '2':
printf("2 Selected\n");
found=true;
strcpy(returnBuffer,"OK\n");
break;
case '3':
printf("3 Selected\n");
found=true;
strcpy(returnBuffer,"OK\n");
break;
default:
printf("Invalid value\n");
break;
}
}
if(strncmp("get",Arguments[COM],3) == 0)
{
printf("Get variable\n");
if( strncmp("value1",Arguments[KEY],6)==0)
{
sprintf(returnBuffer,("Value 1\n"));
found=true;
}
if( strncmp("value2",Arguments[KEY],6)==0)
{
sprintf(returnBuffer,("Value 2\n"));
found=true;
}
}
We now send the message back to the client.
if(!found)
{
sprintf(returnBuffer,("FAIL\n"));
}
printf("Replying with: %s",returnBuffer);
write(client_fd, returnBuffer, strlen(returnBuffer));
fflush(stdout);
Once the command has been processed, the connection is closed.
printf("Closing client connection\n");
close(client_fd);
}
}
}
}