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   1 /* udp_o.c -- read packets from the network */
   2
   3 #include <sys/types.h>
   4 #include <sys/socket.h>
   5 #include <netinet/in.h>
   6 #include <netdb.h>
   7
   8 #include <stdio.h>
   9 #include <string.h>
  10 #include <ctype.h>
  11
  12 #define BUFSIZE 1024
  13 #define UDP_PORT 10094
  14
  15 main(argc, argv)
  16         int argc;
  17         char *argv[];
  18 {
  19         int sock, fromlen, l, i, portno;
  20         char buf[BUFSIZE], *p;
  21         struct sockaddr_in from;
  22
  23         portno = UDP_PORT;
  24
  25         /* Test arguments */
  26         if(argc>2){
  27                 fprintf(stderr,"Usage: %s [<portnumber>]\n",argv[0]);
  28                 exit(1);
  29         }
  30         if(argc>1)portno = atoi(argv[1]);
  31
  32         /* Create socket */
  33         sock = socket(AF_INET, SOCK_DGRAM, 0);
  34         if (sock<0) {
  35                 perror("opening raw socket");
  36                 exit(1);
  37         }
  38
  39         bzero((char *)&from, sizeof from);
  40         from.sin_family = AF_INET;
  41         from.sin_addr.s_addr = htonl(INADDR_ANY);
  42         from.sin_port = htons(portno);
  43         if (bind(sock, (struct sockaddr *)&from, sizeof from) < 0){
  44                 perror("binding UDP socket");
  45                 exit(1);
  46         }
  47
  48         l = 0;
  49         while(l>-1){
  50                 fromlen = sizeof from;
  51                 l = recvfrom(sock, buf, BUFSIZE, 0,
  52                         (struct sockaddr *)&from, &fromlen);
  53                 if(l<0){
  54                         perror("udp socket");
  55                         close(sock);
  56                         exit(2);
  57                 }
  58                 fprintf(stdout,"---------->recv %d bytes from port %d host %s\n", l,
  59                                 ntohs(from.sin_port),
  60                                 (char *)inet_ntoa(from.sin_addr));
  61
  62                 fprintf(stdout,"{%d.%d.%d.%d->%d.%d.%d.%d}\n",buf[12],buf[13],
  63                         buf[14],buf[15],buf[16],buf[17],buf[18],buf[19]);
  64
  65                 for(p=buf+40,i=0;i<(l-40);i++,p++){
  66                         if(isprint(*p))putc(*p,stdout);
  67                         else putc('.',stdout);
  68                 }
  69                                 putc('\n',stdout);
  70                 fflush(stdout);
  71         }
  72
  73         /* all done, close the socket and exit */
  74         close(sock);
  75         exit(0);
  76 }