receiver.c

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <string.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <arpa/inet.h> 
#include <netinet/in.h> 
#include "pthread.h"
#include <inttypes.h>

#include "state.h"

/** Configure this **/
#define LOCAL_HOST "169.254.100.16" // IP of local interface
#define R_PORT 8000

#define REMOTE_HOST "169.254.227.87"
#define S_PORT 8001
/** **/


#define TX_INTERVAL_MS 300
#define STATE_SIZE sizeof(DIJOYSTATE2_t)

void *send_force(void *arg) {
  int8_t force = 0;
  int sockfd;
  struct sockaddr_in servaddr;

  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(S_PORT);
  servaddr.sin_addr.s_addr = inet_addr(REMOTE_HOST);
  
  if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("failed to create socket");
    exit(EXIT_FAILURE);
  }

  while (1) {
    usleep(TX_INTERVAL_MS * 1000);
    printf("Send force %d\n", force);
    force += 5;
    sendto(sockfd, (char*) &force, 1, MSG_CONFIRM,
		    (struct sockaddr *) &servaddr, sizeof(servaddr));

  }
}

int main() {
  int sockfd;
  char buffer[STATE_SIZE + 1];

  struct sockaddr_in servaddr = { 0 };

  if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("failed to create socket");
    exit(EXIT_FAILURE);
  }

  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(R_PORT);
  servaddr.sin_addr.s_addr = inet_addr(LOCAL_HOST);

  if (bind(sockfd, (const struct sockaddr *) &servaddr, 
            sizeof(servaddr)) < 0) {
    perror("bind failed");
    exit(EXIT_FAILURE);
  }

  DIJOYSTATE2_t state;
  char recvbuf[sizeof(DIJOYSTATE2_t) + 4];
  pthread_t send_tid;
  pthread_create(&send_tid, NULL, send_force, NULL);

  while(1) {
    //printf("Wait recv\n");
    int n, len;
    n = recvfrom(sockfd, recvbuf, STATE_SIZE, MSG_WAITALL,
                  (struct sockaddr *) &servaddr, &len);
    uint32_t packet_ct = ((uint32_t*) recvbuf)[0];
    memcpy(&state, recvbuf + 4, sizeof(state));
    printf("Receive state (Pkt: %8X) :  Wheel: %d | Throttle: %d | Brake: %d\n", packet_ct, state.lX, state.lY, state.lRz);
  }

  return 0;
}