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)                       /* read direction of socket has shutdown */
  66                 exit(EXIT_FAILURE);
  67
  68             for (i = 0; i < nev; i++) {
  69                 if (evlist[i].flags & EV_ERROR) {                /* report errors */
  70                     fprintf(stderr, "EV_ERROR: %s\n", strerror(evlist[i].data));
  71                     exit(EXIT_FAILURE);
  72                 }
  73
  74                 if (evlist[i].ident == sckfd) {                  /* we have data from the host */
  75                     memset(buf, 0, BUFSIZE);
  76                     if (read(sckfd, buf, BUFSIZE) < 0)
  77                         diep("read()");
  78                     fputs(buf, stdout);
  79                 }
  80
  81                 else if (evlist[i].ident == fileno(stdin)) {     /* we have data from stdin */
  82                     memset(buf, 0, BUFSIZE);
  83                     fgets(buf, BUFSIZE, stdin);
  84                     sendbuftosck(sckfd, buf, strlen(buf));
  85                 }
  86             }
  87         }
  88     }
  89
  90     /* Close kqueue */
  91     if (close(kq) == -1)
  92         diep("close()");
  93
  94     return EXIT_SUCCESS;
  95 }
  96
  97 void diep(const char *s)
  98 {
  99     perror(s);
 100     exit(EXIT_FAILURE);
 101 }
 102
 103 int tcpopen(const char *host, int port)
 104 {
 105     struct sockaddr_in server;
 106     struct hostent *hp;
 107     int sckfd;
 108
 109     if ((hp = gethostbyname(host)) == NULL)
 110         diep("gethostbyname()");
 111
 112     if ((sckfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
 113         diep("socket()");
 114
 115     server.sin_family = AF_INET;
 116     server.sin_port = htons(port);
 117     server.sin_addr = *((struct in_addr *)hp->h_addr);
 118     memset(&(server.sin_zero), 0, 8);
 119
 120     if (connect(sckfd, (struct sockaddr *)&server, sizeof(struct sockaddr)) < 0)
 121         diep("connect()");
 122
 123     return sckfd;
 124 }
 125
 126 void sendbuftosck(int sckfd, const char *buf, int len)
 127 {
 128     int bytessent, pos;
 129
 130     pos = 0;
 131     do {
 132         if ((bytessent = send(sckfd, buf + pos, len - pos, 0)) < 0)
 133             diep("send()");
 134         pos += bytessent;
 135     } while (bytessent > 0);
 136 }