ast_networks_5e_tcp_client.c

  /* This page contains the client program. The following one contains the
 * server program. Once the server has been compiled and started, clients
 * anywhere on the Internet can send commands (file names) to the server.
 * The server responds by opening and returning the entire file requested.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
 #include <stdio.h>

#define SERVER_PORT 12345   /* arbitrary, but client and server must agree */
#define BUF_SIZE 4096     /* block transfer size */

int main(int argc, char **argv)
{
  int c, s, bytes;
  char buf[BUF_SIZE];     /* buffer for incoming file */
  char obuf[BUF_SIZE];    /* buffer for outgoing file */
  struct hostent *h;      /* info about server */
  struct sockaddr_in channel;   /* holds IP address */

  if (argc != 3) fatal("Usage: client server-name file-name");
  h = gethostbyname(argv[1]);   /* look up host's IP address */
  if (!h) fatal("gethostbyname failed");

  s = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
  if (s < 0) fatal("socket");
  memset(&channel, 0, sizeof(channel));
  channel.sin_family= AF_INET;
  memcpy(&channel.sin_addr.s_addr, h->h_addr, h->h_length);
  channel.sin_port= htons(SERVER_PORT);
  c = connect(s, (struct sockaddr *) &channel, sizeof(channel));
  if (c < 0) fatal("connect failed");

  /* Connection is now established. Send file name including 0 byte at end. */
  write(s, argv[2], strlen(argv[2])+1);

  /* Go get the file and write it to a local file 
     (new or existing, overwritten) of the same name. */
  FILE *dst;

  sprintf(obuf, "out/%s", argv[2]);

  dst = fopen(obuf, "w+");
  while (1) {
        bytes = read(s, buf, BUF_SIZE); /* read from socket */
        if (bytes <= 0) exit(0);  /* check for end of file */
        fwrite(buf, sizeof(char), bytes, dst);
        // write(1, buf, bytes);    /* write to standard output */
  }
  fclose(dst);
}

fatal(char *string)
{
  printf("%s\n", string);
  exit(1);
}

ast_networks_5e_tcp_server.c

#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define SERVER_PORT 12345		/* arbitrary, but client and server must agree */
#define BUF_SIZE 4096			/* block transfer size */
#define QUEUE_SIZE 10

int main(int argc, char *argv[])
{	
  int s, b, l, fd, sa, bytes, on = 1;
  char buf[BUF_SIZE];			/* buffer for outgoing file */
  struct sockaddr_in channel;		/* hold's IP address */

  /* Build address structure to bind to socket. */
  memset(&channel, 0, sizeof(channel));	/* zero channel */
  channel.sin_family = AF_INET;
  channel.sin_addr.s_addr = htonl(INADDR_ANY);
  channel.sin_port = htons(SERVER_PORT);

  /* Passive open. Wait for connection. */
  s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); /* create socket */
  if (s < 0) fatal("socket failed");
  setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on));

  b = bind(s, (struct sockaddr *) &channel, sizeof(channel));
  if (b < 0) fatal("bind failed");

  l = listen(s, QUEUE_SIZE);		/* specify queue size */
  if (l < 0) fatal("listen failed");

  /* Socket is now set up and bound. Wait for connection and process it. */
  while (1) {
        sa = accept(s, 0, 0);		/* block for connection request */
        if (sa < 0) fatal("accept failed");

        read(sa, buf, BUF_SIZE);	/* read file name from socket */

        /* Get and return the file. */
        fd = open(buf, O_RDONLY);	/* open the file to be sent back */
        if (fd < 0) fatal("open failed");

        while (1) {
                bytes = read(fd, buf, BUF_SIZE); /* read from file */
                if (bytes <= 0) break;		 /* check for end of file */
                write(sa, buf, bytes);		 /* write bytes to socket */
        }
        close(fd);				 /* close file */
        close(sa);				 /* close connection */
  }
}

fatal(char *string)
{
  printf("%s", string);
  exit(1);
}