kqueue/kqclient.c

   1 /* compile with:
   2    gcc kqclient.c -o kqclient -Wall -W -Wextra -ansi -pedantic
   3
   4    We will implement a raw tcp client using the kqueue framework.
   5    Whenever the host sends data to the socket, we will print them
   6    in the standard output stream. Similarly, when the user types
   7    something in the standard input stream, we will send it to the
   8    host through the socket.
   9    Basically, we need to monitor the following:
  10
  11    1. any incoming host data in the socket
  12    2. any user data in the standard input stream
  13 */
  14
  15 #include <netinet/in.h>
  16 #include <sys/event.h>
  17 #include <sys/socket.h>
  18 #include <sys/time.h>
  19 #include <netdb.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24
  25 #define BUFSIZE 1024
  26
  27 /* function prototypes */
  28 void diep(const char *s);
  29 int tcpopen(const char *host, int port);
  30 void sendbuftosck(int sckfd, const char *buf, int len);
  31
  32 int main(int argc, char *argv[])
  33 {
  34     struct kevent chlist[2];   /* events we want to monitor */
  35     struct kevent evlist[2];   /* events that were triggered */
  36     char buf[BUFSIZE];
  37     int sckfd, kq, nev, i;
  38
  39     /* check argument count */
  40     if (argc != 3) {
  41         fprintf(stderr, "usage: %s host port\n", argv[0]);
  42         exit(EXIT_FAILURE);
  43     }
  44
  45     /* open a connection to a host:port pair */
  46     sckfd = tcpopen(argv[1], atoi(argv[2]));
  47
  48     /* create a new kernel event queue */
  49     if ((kq = kqueue()) == -1)
  50         diep("kqueue()");
  51
  52     /* initialise kevent structures */
  53     EV_SET(&chlist[0], sckfd, EVFILT_READ, EV_ADD | EV_ENABLE, 0, 0, 0);
  54     EV_SET(&chlist[1], fileno(stdin), EVFILT_READ, EV_ADD | EV_ENABLE, 0, 0, 0);
  55
  56     /* loop forever */
  57     for (;;) {
  58         nev = kevent(kq, chlist, 2, evlist, 2, NULL);
  59
  60         if (nev < 0)
  61             diep("kevent()");
  62
  63         else if (nev > 0) {
  64             if (evlist[0].flags & EV_EOF)                       /* read direction of socket has shutdown */
  65                 exit(EXIT_FAILURE);
  66
  67             for (i = 0; i < nev; i++) {
  68                 if (evlist[i].flags & EV_ERROR) {                /* report errors */
  69                     fprintf(stderr, "EV_ERROR: %s\n", strerror(evlist[i].data));
  70                     exit(EXIT_FAILURE);
  71                 }
  72
  73                 if (evlist[i].ident == sckfd) {                  /* we have data from the host */
  74                     memset(buf, 0, BUFSIZE);
  75                     if (read(sckfd, buf, BUFSIZE) < 0)
  76                         diep("read()");
  77                     fputs(buf, stdout);
  78                 }
  79
  80                 else if (evlist[i].ident == fileno(stdin)) {     /* we have data from stdin */
  81                     memset(buf, 0, BUFSIZE);
  82                     fgets(buf, BUFSIZE, stdin);
  83                     sendbuftosck(sckfd, buf, strlen(buf));
  84                 }
  85             }
  86         }
  87     }
  88
  89     close(kq);
  90     return EXIT_SUCCESS;
  91 }
  92
  93 void diep(const char *s)
  94 {
  95     perror(s);
  96     exit(EXIT_FAILURE);
  97 }
  98
  99 int tcpopen(const char *host, int port)
 100 {
 101     struct sockaddr_in server;
 102     struct hostent *hp;
 103     int sckfd;
 104
 105     if ((hp = gethostbyname(host)) == NULL)
 106         diep("gethostbyname()");
 107
 108     if ((sckfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
 109         diep("socket()");
 110
 111     server.sin_family = AF_INET;
 112     server.sin_port = htons(port);
 113     server.sin_addr = *((struct in_addr *)hp->h_addr);
 114     memset(&(server.sin_zero), 0, 8);
 115
 116     if (connect(sckfd, (struct sockaddr *)&server, sizeof(struct sockaddr)) < 0)
 117         diep("connect()");
 118
 119     return sckfd;
 120 }
 121
 122 void sendbuftosck(int sckfd, const char *buf, int len)
 123 {
 124     int bytessent, pos;
 125
 126     pos = 0;
 127     do {
 128         if ((bytessent = send(sckfd, buf + pos, len - pos, 0)) < 0)
 129             diep("send()");
 130         pos += bytessent;
 131     } while (bytessent > 0);
 132 }