polaris% num http_cli.c

   1  /* http_cli.c
   2     This is a client program for getting http service.
     
   3     Algorithm outline:
   4       a. Open a TCP socket.
   5       b. Initialize server socket address structure
   6       c. Connect to server
   7       d. Send user input to server
   8       e. Loop around to display server responses on screen
   9       f. Close socket.
     
  10     This program also illustrates:
  11       a. Use of gethostbyname() to get some infor. on intended server.
  12       b. Use of bcopy() to copy an element into a structure.
     
  13     Note: This client program accepts only one client request, no pipelining.
     
  14     To compile:       gcc -o http_cli http_cli.c -lsocket -lnsl 
  15     Command syntax:   http_cli  server_name (either DNS or IP)
     
  16                                                            Sam Hsu 
  17  */
     
  18  #include <stdio.h>
  19  #include <unistd.h> 
  20  #include <sys/types.h> 
  21  #include <sys/socket.h>
  22  #include <netinet/in.h>
  23  #include <netdb.h>
  24  #define  SER_PORT  80     /* Official HTTP port  */
     
  25  main(int argc, char *argv[])
  26  {
  27    int cli_sock, ser_len, offset;
  28    ssize_t nread;
  29    char buf[BUFSIZ], stdinbuf[BUFSIZ/2];
  30    struct sockaddr_in  ser;
  31    struct hostent *ser_info;
     
  32            /* to open a socket */
  33    if ((cli_sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)  {
  34        fprintf(stderr, "Unable to create socket for client\n");
  35        exit(1);
  36    }
  37            /* to initialize server sockaddr_in structure */
  38    ser_len = sizeof(ser);            /* to get ser length */
  39    bzero((char *)&ser, ser_len);     /* to zero out struct */
  40    ser.sin_family      = AF_INET;    /* Internet domain */
  41    ser.sin_port = htons(SER_PORT);   /* echo server port number */
  42            /* to get some infor about the remote server */
  43    if ((ser_info = gethostbyname(argv[1])) == (struct hostent *)NULL) {
  44        fprintf(stderr, "unknown server\n");
  45        exit(1);
  46    }
  47    bcopy((char *)ser_info->h_addr, (char *)&ser.sin_addr, ser_info->h_length);
     
  48            /* to connect to server */
  49    if ((connect(cli_sock, (struct sockaddr *)&ser, ser_len)) == -1) {
  50        fprintf(stderr, "can't connect to  server\n");
  51        exit(1);
  52    }
     
  53    offset = 0;   /* get user input & assemble a request */
  54    while (fgets(stdinbuf, BUFSIZ/2, stdin)) {  /* no error checking */
  55        nread = strlen(stdinbuf);             /* see how many char's read */
  56        strncpy(&buf[offset], stdinbuf, nread); /* copy to send buffer */
  57        offset += (int)nread;                 /* update offset */
  58        if (strlen(stdinbuf) == 1) {          /* just a '\n' by itself */
  59            nread = (ssize_t)offset;          /* total num of char's read */ 
  60            break;
  61        }
  62    }
  63    send(cli_sock, buf, (size_t)nread, 0);     /* send request to server */
     
  64    again:                                     /* a branch label for looping */
  65        nread = recv(cli_sock, buf, BUFSIZ, 0); /* get response from server */ 
  66    if (nread > 0) {                            /* if some data received */
  67        write(STDOUT_FILENO, buf, (size_t)nread);  /* display it on screen */
  68        goto again;                             /* not supposed to, but ...*/
  69    } 
     
  70    close(cli_sock);
  71  }  /* main */

polaris% http_cli www.cse.fau.edu
HEAD / http/1.1
Connection: close
Host: www.cse.fau.edu

HTTP/1.1 200 OK
Date: Tue, 01 Nov 2005 23:14:32 GMT
Server: Apache/2.0.48 (Unix) mod_ssl/2.0.48 OpenSSL/0.9.7c DAV/2 PHP/4.3.4
Last-Modified: Thu, 08 Sep 2005 06:27:29 GMT
ETag: "450923-11df-c15d5640"
Accept-Ranges: bytes
Content-Length: 4575
Connection: close
Content-Type: text/html; charset=ISO-8859-1