#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <sys/un.h>#include <string.h>#include <errno.h>#define LISTENQ	5int main(int argc, char **argv){  int fd;  if (argc < 2)  {    fprintf(stdout, "Usage: %s <path>\n", argv[0]);    exit(1);  }  // XXX: step 1, socket();  //int socket(int domain, int type, int protocol);  if ((fd = socket(PF_LOCAL, SOCK_STREAM, 0)) < 0)  {    fprintf(stderr, "socket() failed: %s\n", strerror(errno));    exit(1);  }  unlink(argv[1]);  // XXX: step 2, bind() (optional)  struct sockaddr_un local_address;  memset(&local_address, 0, sizeof(local_address));  local_address.sun_family = PF_LOCAL;  memcpy(local_address.sun_path, argv[1], strlen(argv[1]));  //int bind(int sockfd, struct sockaddr *my_addr, socklen_t addrlen);  if (bind(fd, (struct sockaddr *) &local_address, sizeof(local_address)) < 0)  {    fprintf(stderr, "bind() failed: %s\n", strerror(errno));    // FIXME:    close(fd);    exit(1);  }  // XXX: step 3, listen();  // int listen(int s, int backlog);  if (listen(fd, LISTENQ) < 0)  {    fprintf(stderr, "listen() failed: %s\n", strerror(errno));    // FIXME:    close(fd);    exit(1);  }  // XXX: step 4, accept();  int new_accepted_socket;  struct sockaddr_un peer_address;  socklen_t peer_address_length;  ssize_t written;  char *welcome_message = "welcome to unix domain programming.";  for (;;)  {    peer_address_length = sizeof(peer_address);    //int accept(int s, struct sockaddr *addr, socklen_t *addrlen);    if ((new_accepted_socket = accept(fd, (struct sockaddr *) &peer_address, &peer_address_length)) < 0)    {      fprintf(stderr, "accept() failed: %s\n", strerror(errno));      // FIXME:      close(fd);      exit(1);    }    fprintf(stdout, "Accepted new connection %d from %s.\n", new_accepted_socket, peer_address.sun_path);    // XXX: step 4, r/w    // FIXME: maybe we should use a loop to write all data to client    //ssize_t write(int fd, const void *buf, size_t count);    if ((written = write(new_accepted_socket, welcome_message, strlen(welcome_message))) < 0)    {      fprintf(stderr, "write() failed: %s\n", strerror(errno));      // FIXME:      close(new_accepted_socket);      close(fd);      exit(1);    }    else    {      fprintf(stdout, "written %d bytes to %d.\n", written, new_accepted_socket);    }    close(new_accepted_socket);  }  // XXX: step 5, close()  close(fd);  return 0;}