kqueue/kqclient.c

   1 /*
   2  * Compile with:
   3  * gcc kqclient.c -o kqclient -Wall -W -Wextra -ansi -pedantic
   4  *
   5  * We will implement a raw tcp client using the kqueue framework.
   6  * Whenever the host sends data to the socket, we will print them
   7  * in the standard output stream. Similarly, when the user types
   8  * something in the standard input stream, we will send it to the
   9  * host through the socket.
  10  * Basically, we need to monitor the following:
  11  *
  12  * 1. any incoming host data in the socket
  13  * 2. any user data in the standard input stream
  14 */
  15
  16 #include <netinet/in.h>
  17 #include <sys/event.h>
  18 #include <sys/socket.h>
  19 #include <sys/time.h>
  20 #include <netdb.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25
  26 #define BUFSIZE 1024
  27
  28 /* Function prototypes */
  29 void diep(const char *s);
  30 int tcpopen(const char *host, int port);
  31 void sendbuftosck(int sckfd, const char *buf, int len);
  32
  33 int main(int argc, char *argv[])
  34 {
  35     struct kevent chlist[2];   /* events we want to monitor */
  36     struct kevent evlist[2];   /* events that were triggered */
  37     char buf[BUFSIZE];
  38     int sckfd, kq, nev, i;
  39
  40     /* Check argument count */
  41     if (argc != 3) {
  42         fprintf(stderr, "Usage: %s host port\n", argv[0]);
  43         exit(EXIT_FAILURE);
  44     }
  45
  46     /* Open a connection to a host:port pair */
  47     sckfd = tcpopen(argv[1], atoi(argv[2]));
  48
  49     /* Create a new kernel event queue */
  50     if ((kq = kqueue()) == -1)
  51         diep("kqueue()");
  52
  53     /* Initialise kevent structures */
  54     EV_SET(&chlist[0], sckfd, EVFILT_READ, EV_ADD | EV_ENABLE, 0, 0, 0);
  55     EV_SET(&chlist[1], fileno(stdin), EVFILT_READ, EV_ADD | EV_ENABLE, 0, 0, 0);
  56
  57     /* Loop forever */
  58     for (;;) {
  59         nev = kevent(kq, chlist, 2, evlist, 2, NULL);
  60
  61         if (nev < 0)
  62             diep("kevent()");
  63
  64         else if (nev > 0) {
  65             if (evlist[0].flags & EV_EOF)
  66                 /* Read direction of socket has shutdown */
  67                 exit(EXIT_FAILURE);
  68
  69             for (i = 0; i < nev; i++) {
  70                 if (evlist[i].flags & EV_ERROR) {
  71                     /* Report errors */
  72                     fprintf(stderr, "EV_ERROR: %s\n", strerror(evlist[i].data));
  73                     exit(EXIT_FAILURE);
  74                 }
  75
  76                 if (evlist[i].ident == sckfd) {
  77                     /* We have data from the host */
  78                     memset(buf, 0, BUFSIZE);
  79                     if (read(sckfd, buf, BUFSIZE) < 0)
  80                         diep("read()");
  81                     fputs(buf, stdout);
  82                 }
  83
  84                 else if (evlist[i].ident == fileno(stdin)) {
  85                     /* We have data from stdin */
  86                     memset(buf, 0, BUFSIZE);
  87                     fgets(buf, BUFSIZE, stdin);
  88                     sendbuftosck(sckfd, buf, strlen(buf));
  89                 }
  90             }
  91         }
  92     }
  93
  94     /* Close kqueue */
  95     if (close(kq) == -1)
  96         diep("close()");
  97
  98     return EXIT_SUCCESS;
  99 }
 100
 101 void diep(const char *s)
 102 {
 103     perror(s);
 104     exit(EXIT_FAILURE);
 105 }
 106
 107 int tcpopen(const char *host, int port)
 108 {
 109     struct sockaddr_in server;
 110     struct hostent *hp;
 111     int sckfd;
 112
 113     if ((hp = gethostbyname(host)) == NULL)
 114         diep("gethostbyname()");
 115
 116     if ((sckfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
 117         diep("socket()");
 118
 119     server.sin_family = AF_INET;
 120     server.sin_port = htons(port);
 121     server.sin_addr = *((struct in_addr *)hp->h_addr);
 122     memset(&(server.sin_zero), 0, 8);
 123
 124     if (connect(sckfd, (struct sockaddr *)&server, sizeof(struct sockaddr)) < 0)
 125         diep("connect()");
 126
 127     return sckfd;
 128 }
 129
 130 void sendbuftosck(int sckfd, const char *buf, int len)
 131 {
 132     int bytessent, pos;
 133
 134     pos = 0;
 135     do {
 136         if ((bytessent = send(sckfd, buf + pos, len - pos, 0)) < 0)
 137             diep("send()");
 138         pos += bytessent;
 139     } while (bytessent > 0);
 140 }