#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <sys/select.h>#include <sys/time.h>#include <arpa/inet.h>#include <string.h>#include <errno.h>#include "utils.h"#include "link.h"//////////////////////////////////////////////////////////////////////// Macro definitions//////////////////////////////////////////////////////////////////////#define BUFFER_SIZE	1024//////////////////////////////////////////////////////////////////////// Global variables//////////////////////////////////////////////////////////////////////int global_chat_service_socket;fd_set global_read_set;fd_set global_write_set;fd_set global_except_set;int global_max_fd = 0;link_t *global_client_links;//////////////////////////////////////////////////////////////////////// Function prototypes//////////////////////////////////////////////////////////////////////void network_init(void);void network_register_read(int fd);void network_register_write(int fd);void network_register_except(int fd);void network_unregister_read(int fd);void network_unregister_write(int fd);void network_unregister_except(int fd);void data_exchange(char *message, unsigned long length);static void local_destroy_data(void *p);static void local_dump_node(void *p);//////////////////////////////////////////////////////////////////////// Functions//////////////////////////////////////////////////////////////////////int main(int argc, char **argv){  if (argc < 3)  {    fprintf(stdout, "Usage: %s <ip> <port>\n", argv[0]);    exit(1);  }  global_client_links = link_init(local_destroy_data, local_dump_node);  // XXX:step 1, socket();  //int socket(int domain, int type, int protocol);  if ((global_chat_service_socket = socket(PF_INET, SOCK_DGRAM, 0)) < 0)  {    fprintf(stderr, "Create a new UDP socket failed: %s\n", strerror(errno));    exit(1);  }  // XXX:step 2, bind();  struct sockaddr_in server_address;  memset(&server_address, 0, sizeof(server_address));  server_address.sin_family = PF_INET;  server_address.sin_port = htons(atoi(argv[2]));  server_address.sin_addr.s_addr = inet_addr(argv[1]);  // int bind(int sockfd, struct sockaddr *my_addr, socklen_t addrlen);  if (bind(global_chat_service_socket, (struct sockaddr *) &server_address, sizeof(server_address)) < 0)  {    fprintf(stderr, "bind() failed: %s\n", strerror(errno));    exit(1);  }  network_init();  network_register_read(global_chat_service_socket);  fd_set rset, wset, eset;  int n;  struct timeval to;  for (;;)  {    rset = global_read_set;    wset = global_write_set;    eset = global_except_set;    to.tv_sec = 1;    to.tv_usec = 0;    // XXX:step 3, recvfrom()/sendto    //int select(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);    if ((n = select(global_max_fd + 1, &rset, &wset, &eset, &to)) < 0)    {      if (errno == EINTR)      {	continue;      }      else      {	fprintf(stderr, "select() failed: %s\n", strerror(errno));	// FIXME:       }    }    else if (n == 0)    {      // TODO: do something here.      fprintf(stdout, "timeout ...\n");    }    else    {      if (FD_ISSET(global_chat_service_socket, &rset))      {	char buffer[BUFFER_SIZE];	struct sockaddr_in peer_address;	socklen_t peer_address_length;	ssize_t n;	peer_address_length = sizeof(peer_address);      again:	// ssize_t recvfrom(int s, void *buf, size_t len, int flags, struct sockaddr *from, socklen_t *fromlen);	if ((n = recvfrom(global_chat_service_socket, buffer, BUFFER_SIZE, 0, (struct sockaddr *) &peer_address, &peer_address_length)) < 0)	{	  if (errno == EINTR)	  {	    goto again;	  }	  else	  {	    fprintf(stderr, "recvfrom() failed: %s\n", strerror(errno));	    // FIXME: error handler	  }	}	else	{	  fprintf(stdout, "INFO: read %d bytes from %s:%d\n", n, inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));#if 0	  int i;	  for (i = 0; i < n; i++)	  {	    fprintf(stdout, "0x%x", buffer[i]);	  }#endif	  buffer[n] = '\0';	  fprintf(stdout, "DEBUG: %s\n", buffer);	  link_node_t *node;	  node = create_node(NODE_TYPE_NORMAL);	  if ((node->data = (void *) malloc(sizeof(struct sockaddr_in))) == NULL)	  {	    fprintf(stderr, "Allocate memory failed: %s\n", strerror(errno));	    // FIXME: error handler	  }	  else	  {	    // FIXME: check existed client object	    *((struct sockaddr_in *) node->data) = peer_address;	  }	  link_insert_node(global_client_links, global_client_links, node, INSERT_METHOD_AFTER);	  data_exchange(buffer, n);	}      }    }  }  // XXX: step 4, close()  close(global_chat_service_socket);  link_destroy(global_client_links);  return 0;}void data_exchange(char *message, unsigned long length){  link_node_t *p;  link_node_t *current;  p = global_client_links;  link_dump_nodes(global_client_links);  struct sockaddr_in peer_address;  while (p && p->next)  {    current = p;    p = current->next;    fprintf(stdout, "DEBUG: current = %p, current->type = %d\n", current, current->type);    if (current->type == NODE_TYPE_NORMAL)    {      // FIXME: check return value      peer_address = *(struct sockaddr_in *) current->data;      // ssize_t  sendto(int  s,  const  void  *buf,  size_t len, int flags, const struct sockaddr *to, socklen_t tolen);      sendto(global_chat_service_socket, message, length, 0, (struct sockaddr *) &peer_address, sizeof(peer_address));      fprintf(stdout, "forwarding data to %s:%d\n", inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));    }  }  if (p->type == NODE_TYPE_NORMAL)  {    peer_address = *(struct sockaddr_in *) p->data;    // FIXME: check return value    // ssize_t  sendto(int  s,  const  void  *buf,  size_t len, int flags, const struct sockaddr *to, socklen_t tolen);    sendto(global_chat_service_socket, message, length, 0, (struct sockaddr *) &peer_address, sizeof(peer_address));    fprintf(stdout, "forwarding data to %s:%d\n", inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));  }}void network_init(void){  FD_ZERO(&global_read_set);  FD_ZERO(&global_write_set);  FD_ZERO(&global_except_set);  global_max_fd = 0;}void network_register_read(int fd){  //void FD_SET(int fd, fd_set * fdset);  FD_SET(fd, &global_read_set);  if (fd > global_max_fd)  {    global_max_fd = fd;  }}void network_unregister_read(int fd){  FD_CLR(fd, &global_read_set);}void network_register_write(int fd){  //void FD_SET(int fd, fd_set * fdset);  FD_SET(fd, &global_write_set);  if (fd > global_max_fd)  {    global_max_fd = fd;  }}void network_unregister_write(int fd){  FD_CLR(fd, &global_write_set);}void network_register_except(int fd){  //void FD_SET(int fd, fd_set * fdset);  FD_SET(fd, &global_except_set);  if (fd > global_max_fd)  {    global_max_fd = fd;  }}void network_unregister_except(int fd){  FD_CLR(fd, &global_except_set);}static void local_destroy_data(void *p){  safe_free(p);}static void local_dump_node(void *p){  if (!p)  {    return;  }  fprintf(stdout, "DEBUG: try to dump %p\n", p);  link_node_t *node = (link_node_t *) p;  if (get_node_type(node) == NODE_TYPE_HEAD)  {    //fprintf(stdout, "HEAD:\n");  }  else if (get_node_type(node) == NODE_TYPE_TAIL)  {    //fprintf(stdout, "TAIL:\n");  }  else  {    struct sockaddr_in peer_address;    peer_address = *(struct sockaddr_in *) node->data;    fprintf(stdout, "Normal: %s:%d\n", inet_ntoa(peer_address.sin_addr), ntohs(peer_address.sin_port));  }}