client.c

/* Author : Thed Arthur TD, January 2026 */

#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

#define BUFFER_SIZE 1024

int main(int argc, char *argv[]){
  if(argc < 4){
    printf("Usage: %s <OPERATION> <OP1> <OP2> [REGISTRY_IP] [REGISTRY_PORT]\n",
           argv[0]);
    printf("Example: %s ADD 10 20\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  char *op = argv[1];
  int op1 = atoi(argv[2]);
  int op2 = atoi(argv[3]);

  char *registry_ip = "127.0.0.1";
  int registry_port = 5000;

  if(argc >= 5)
    registry_ip = argv[4];
  if(argc >= 6)
    registry_port = atoi(argv[5]);

  int sockfd;
  struct sockaddr_in servaddr;

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

  memset(&servaddr, 0, sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(registry_port);
  if(inet_pton(AF_INET, registry_ip, &servaddr.sin_addr) <= 0){
    perror("Invalid address/ Address not supported");
    exit(EXIT_FAILURE);
  }

  struct timeval tv;
  tv.tv_sec = 5;
  tv.tv_usec = 0;
  if(setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0){
    perror("setsockopt");
    close(sockfd);
    exit(EXIT_FAILURE);
  }

  char buffer[BUFFER_SIZE];
  snprintf(buffer, sizeof(buffer), "CLIENT_TASK:%s:%d:%d", op, op1, op2);

  printf("[Client] Sending: %s to %s:%d\n", buffer, registry_ip, registry_port);

  sendto(sockfd, (const char *)buffer, strlen(buffer), 0,
         (const struct sockaddr *)&servaddr, sizeof(servaddr));

  printf("[Client] Waiting for response...\n");

  socklen_t len;
  int n = recvfrom(sockfd, (char *)buffer, BUFFER_SIZE, 0,
                   (struct sockaddr *)&servaddr, &len);

  if(n < 0){
    perror("recvfrom timeout or error");
  } 
  else{
    buffer[n] = '\0';
    printf("[Client] Received: %s\n", buffer);
  }

  close(sockfd);
  return 0;
}