linux下的telnet客户端完整实现源码（c语言）

/* telnet.c - telnet */ #include <sys/types.h> #include <sys/socket.h> #include <sys/time.h> #include <sys/signal.h> #include <sys/errno.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <stdio.h> #include "local.h" void rcvurg(int); #define BUFSIZE 2048 /* read buffer size */ struct termios oldtty; int connect_TCP(const char *host, int port); int ttysetup(void); /*------------------------------------------------------------------------ * telnet - do the TELNET protocol to the given host and port *------------------------------------------------------------------------ */ int telnet(const char *host, int port) { unsigned char buf[BUFSIZE]; int s, nfds; /* socket and # file descriptors */ int cc; int on = 1; fd_set arfds, awfds, rfds, wfds; FILE *sfp; s = connect_TCP(host, port); ttysetup(); fsmbuild(); /* set up FSM's */ (void) signal(SIGURG, rcvurg); (void) setsockopt(s, SOL_SOCKET, SO_OOBINLINE, (char *)&on, sizeof(on)); nfds = getdtablesize(); FD_ZERO(&arfds); FD_ZERO(&awfds); FD_SET(s, &arfds); /* the socket */ FD_SET(0, &arfds); /* standard input */ sfp = fdopen(s, "w"); /* to get buffered output */ while (1) { memcpy(&rfds, &arfds, sizeof(rfds)); memcpy(&wfds, &awfds, sizeof(rfds)); if (select(nfds, &rfds, &wfds, (fd_set *)0, (struct timeval *)0) < 0) { if (errno == EINTR) continue; /* just a signal */ cerrexit("select: %s\n", strerror(errno)); } if (FD_ISSET(s, &rfds)) { cc = read(s, (char *)buf, sizeof(buf)); if (cc < 0) cerrexit("socket read: %s\n", strerror(errno)); else if (cc == 0) { printf("\nconnection closed.\n"); if (tcsetattr(0, TCSADRAIN, &oldtty) < 0) errexit("tcsetattr: %s\n", strerror(errno)); exit(0); } else ttwrite(sfp, stdout, buf, cc); } if (FD_ISSET(0, &rfds)) { cc = read(0, (char *)buf, sizeof(buf)); if (cc < 0) cerrexit("tty read: %s\n", strerror(errno)); else if (cc == 0) { FD_CLR(0, &arfds); (void) shutdown(s, 1); } else sowrite(sfp, stdout, buf, cc); } (void) fflush(sfp); (void) fflush(stdout); } }