snipplets.dev/code/C/unixsocket/client.c

// https://systemprogrammingatntu.github.io/mp2/unix_socket.html

#define SOCKET_NAME "/tmp/resol.sock"
#define BUFFER_SIZE 12

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
  struct sockaddr_un addr;
  int i;
  int ret;
  int data_socket;
  char buffer[BUFFER_SIZE];

  /* Create local socket. */
  data_socket = socket(AF_UNIX, SOCK_STREAM, 0);
  if (data_socket == -1) {
    perror("socket");
    exit(EXIT_FAILURE);
  }

  /*
   * For portability clear the whole structure, since some
   * implementations have additional (nonstandard) fields in
   * the structure.
   */
  memset(&addr, 0, sizeof(struct sockaddr_un));

  /* Connect socket to socket address */
  addr.sun_family = AF_UNIX;
  strncpy(addr.sun_path, SOCKET_NAME, sizeof(addr.sun_path) - 1);

  ret = connect(data_socket, (const struct sockaddr *)&addr, sizeof(struct sockaddr_un));
  if (ret == -1) {
    fprintf(stderr, "The server is down.\n");
    exit(EXIT_FAILURE);
  }

  /* Send arguments. */
  for (i = 1; i < argc; ++i) {
    ret = write(data_socket, argv[i], strlen(argv[i]) + 1);
    if (ret == -1) {
      perror("write");
      break;
    }
  }

  /* Request result. */
  strcpy(buffer, "END");
  ret = write(data_socket, buffer, strlen(buffer) + 1);
  if (ret == -1) {
    perror("write");
    exit(EXIT_FAILURE);
  }

  /* Receive result. */
  ret = read(data_socket, buffer, BUFFER_SIZE);
  if (ret == -1) {
    perror("read");
    exit(EXIT_FAILURE);
  }

  /* Ensure buffer is 0-terminated. */
  buffer[BUFFER_SIZE - 1] = 0;

  printf("Result = %s\n", buffer);

  /* Close socket. */
  close(data_socket);

  exit(EXIT_SUCCESS);
}