Unix Sockets 简明教程

# This represents a comments in /etc/hosts file.
127.0.0.1       localhost
192.217.44.207  nalanda metro
153.110.31.18   netserve
153.110.31.19   mainserver centeral
153.110.31.20   samsonite
64.202.167.10   ns3.secureserver.net
64.202.167.97   ns4.secureserver.net
66.249.89.104   www.google.com
68.178.157.132  services.amrood.com

struct sockaddr {
   unsigned short   sa_family;
   char             sa_data[14];
};

struct sockaddr_in {
   short int            sin_family;
   unsigned short int   sin_port;
   struct in_addr       sin_addr;
   unsigned char        sin_zero[8];
};

struct in_addr {
   unsigned long s_addr;
};

struct hostent {
   char *h_name;
   char **h_aliases;
   int h_addrtype;
   int h_length;
   char **h_addr_list

#define h_addr  h_addr_list[0]
};

struct servent {
   char  *s_name;
   char  **s_aliases;
   int   s_port;
   char  *s_proto;
};

struct servent {
   char  *s_name;
   char  **s_aliases;
   int   s_port;
   char  *s_proto;
};

#include <stdio.h>

int main(int argc, char **argv) {

   union {
      short s;
      char c[sizeof(short)];
   }un;

   un.s = 0x0102;

   if (sizeof(short) == 2) {
      if (un.c[0] == 1 && un.c[1] == 2)
         printf("big-endian\n");

      else if (un.c[0] == 2 && un.c[1] == 1)
         printf("little-endian\n");

      else
         printf("unknown\n");
   }
   else {
      printf("sizeof(short) = %d\n", sizeof(short));
   }

   exit(0);
}

$> gcc byteorder.c
$> ./a.out
little-endian
$>

#include <arpa/inet.h>

(...)

   int retval;
   struct in_addr addrptr

   memset(&addrptr, '\0', sizeof(addrptr));
   retval = inet_aton("68.178.157.132", &addrptr);

(...)

#include <arpa/inet.h>

(...)

   struct sockaddr_in dest;

   memset(&dest, '\0', sizeof(dest));
   dest.sin_addr.s_addr = inet_addr("68.178.157.132");

(...)

#include <arpa/inet.h>

(...)

   char *ip;

   ip = inet_ntoa(dest.sin_addr);

   printf("IP Address is: %s\n",ip);

(...)

#include <sys/types.h>
#include <sys/socket.h>

int socket (int family, int type, int protocol);

#include <sys/types.h>
#include <sys/socket.h>

int connect(int sockfd, struct sockaddr *serv_addr, int addrlen);

#include <sys/types.h>
#include <sys/socket.h>

int bind(int sockfd, struct sockaddr *my_addr,int addrlen);

#include <sys/types.h>
#include <sys/socket.h>

int listen(int sockfd,int backlog);

#include <sys/types.h>
#include <sys/socket.h>

int accept (int sockfd, struct sockaddr *cliaddr, socklen_t *addrlen);

int send(int sockfd, const void *msg, int len, int flags);

int recv(int sockfd, void *buf, int len, unsigned int flags);

int sendto(int sockfd, const void *msg, int len, unsigned int flags, const struct sockaddr *to, int tolen);

int recvfrom(int sockfd, void *buf, int len, unsigned int flags struct sockaddr *from, int *fromlen);

int close( int sockfd );

int shutdown(int sockfd, int how);

 int select(int  nfds, fd_set  *readfds, fd_set  *writefds, fd_set *errorfds, struct timeval *timeout);

fd_set fds;

struct timeval tv;

/* do socket initialization etc.
tv.tv_sec = 1;
tv.tv_usec = 500000;

/* tv now represents 1.5 seconds */
FD_ZERO(&fds);

/* adds sock to the file descriptor set */
FD_SET(sock, &fds);

/* wait 1.5 seconds for any data to be read from any single socket */
select(sock+1, &fds, NULL, NULL, &tv);

if (FD_ISSET(sock, &fds)) {
   recvfrom(s, buffer, buffer_len, 0, &sa, &sa_len);
   /* do something */
}
else {
   /* do something else */
}

#include <unistd.h>

int write(int fildes, const void *buf, int nbyte);

#include <unistd.h>

int read(int fildes, const void *buf, int nbyte);

#include <sys/types.h>
#include <unistd.h>

int fork(void);

void bzero(void *s, int nbyte);

int bcmp(const void *s1, const void *s2, int nbyte);

void bcopy(const void *s1, void *s2, int nbyte);

void *memset(void *s, int c, int nbyte);

#include <stdio.h>
#include <stdlib.h>

#include <netdb.h>
#include <netinet/in.h>

#include <string.h>

void doprocessing (int sock);

int main( int argc, char *argv[] ) {
   int sockfd, newsockfd, portno, clilen;
   char buffer[256];
   struct sockaddr_in serv_addr, cli_addr;
   int n, pid;

   /* First call to socket() function */
   sockfd = socket(AF_INET, SOCK_STREAM, 0);

   if (sockfd < 0) {
      perror("ERROR opening socket");
      exit(1);
   }

   /* Initialize socket structure */
   bzero((char *) &serv_addr, sizeof(serv_addr));
   portno = 5001;

   serv_addr.sin_family = AF_INET;
   serv_addr.sin_addr.s_addr = INADDR_ANY;
   serv_addr.sin_port = htons(portno);

   /* Now bind the host address using bind() call.*/
   if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
      perror("ERROR on binding");
      exit(1);
   }

   /* Now start listening for the clients, here
      * process will go in sleep mode and will wait
      * for the incoming connection
   */

   listen(sockfd,5);
   clilen = sizeof(cli_addr);

   while (1) {
      newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);

      if (newsockfd < 0) {
         perror("ERROR on accept");
         exit(1);
      }

      /* Create child process */
      pid = fork();

      if (pid < 0) {
         perror("ERROR on fork");
         exit(1);
      }

      if (pid == 0) {
         /* This is the client process */
         close(sockfd);
         doprocessing(newsockfd);
         exit(0);
      }
      else {
         close(newsockfd);
      }

   } /* end of while */
}

void doprocessing (int sock) {
   int n;
   char buffer[256];
   bzero(buffer,256);
   n = read(sock,buffer,255);

   if (n < 0) {
      perror("ERROR reading from socket");
      exit(1);
   }

   printf("Here is the message: %s\n",buffer);
   n = write(sock,"I got your message",18);

   if (n < 0) {
      perror("ERROR writing to socket");
      exit(1);
   }

}