#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <termios.h> #include <string.h> #define DO 0xfd #define WONT 0xfc #define WILL 0xfb #define DONT 0xfe #define CMD 0xff #define CMD_ECHO 1 #define CMD_WINDOW_SIZE 31 #define IAC 255 #define SB 250 #define SE 240 #define BUFLEN 200 #define ESCAPE 27 #define SA struct sockaddr static struct termios tin; static void terminal_set(void); static void terminal_reset(void); void negotiate(int sock, unsigned char *buf, int len); void connect_to_server(int sock, int port, char *address); int main(int argc, char *argv[]) { int sock; unsigned char buf[BUFLEN + 1]; int len; int i; int port = 23; if (argc < 2 || argc > 3) { printf("Usage: %s address [port]\n", argv[0]); return 1; } if (argc == 3) port = atoi(argv[2]); // Create socket sock = socket(AF_INET, SOCK_STREAM, 0); if (sock == -1) { perror("Could not create socket. Error"); return 1; } printf("Trying %s...\n", argv[1]); connect_to_server(sock, port, argv[1]); printf("Connected to %s\n", argv[1]); puts("Escape character is '^]'."); // set terminal terminal_set(); atexit(terminal_reset); // 1 second struct timeval ts; ts.tv_sec = 1; ts.tv_usec = 0; while (1) { // select setup fd_set fds; FD_ZERO(&fds); if (sock != 0) FD_SET(sock, &fds); FD_SET(0, &fds); // wait for data int nready = select(sock + 1, &fds, (fd_set *) 0, (fd_set *) 0, &ts); if (nready < 0) { perror("select. Error"); return 1; } else if (nready == 0) { ts.tv_sec = 1; ts.tv_usec = 0; } else if (sock != 0 && FD_ISSET(sock, &fds)) { // start by reading a single byte int rv; if ((rv = recv(sock, buf, 1, 0)) < 0) return 1; else if (rv == 0) { printf("Connection closed by the remote end\n\r"); return 0; } if (buf[0] == CMD) { // read 2 more bytes len = recv(sock, buf + 1, 2, 0); if (len < 0) return 1; else if (len == 0) { printf("Connection closed by the remote end\n\r"); return 0; } negotiate(sock, buf, 3); } else { len = 1; buf[len] = '\0'; printf("%s", buf); fflush(stdout); } } else if (FD_ISSET(0, &fds)) { static char crlf[] = { '\r', '\n' }; buf[0] = getc(stdin); //fgets(buf, 1, stdin); if (buf[0] == '\n') { // with the terminal in raw mode we need to force a LF if (send(sock, crlf, 1, 0) < 0) { return 1; } } else if (buf[0] == ESCAPE) { printf("Connection closed by the client end\n\r"); return 0; } else { if (send(sock, buf, 1, 0) < 0) return 1; } } } close(sock); return 0; } void negotiate(int sock, unsigned char *buf, int len) { int i; const char* option_code[350]; option_code[00] = "TRANSMIT-BINARY"; option_code[01] = "ECHO"; option_code[03] = "SUPPRESS-GO-AHEAD"; option_code[05] = "STATUS"; option_code[06] = "TIMING-MARK"; option_code[10] = "NAOCRD"; option_code[11] = "NAOHTS"; option_code[12] = "NAOHTD"; option_code[13] = "NAOFFD"; option_code[14] = "NAOVTS"; option_code[15] = "NAOVTD"; option_code[16] = "NAOLFD"; option_code[17] = "EXTEND-ASCII"; option_code[18] = "LOGOUT"; option_code[19] = "BM"; option_code[20] = "DET"; option_code[23] = "SEND-LOCATION"; option_code[24] = "TERMINAL-TYPE"; option_code[25] = "END-OF-RECORD"; option_code[26] = "TUID"; option_code[27] = "OUTMRK"; option_code[28] = "TTYLOC"; option_code[29] = "3270-REGIME"; option_code[30] = "X.3-PAD"; option_code[31] = "NAWS"; option_code[32] = "TERMINAL-SPEED"; option_code[33] = "TOGGLE-FLOW-CONTROL"; option_code[34] = "LINEMODE"; option_code[35] = "X-DISPLAY-LOCATION"; option_code[36] = "ENVIRON"; option_code[37] = "AUTHENTICATION"; option_code[38] = "ENCRYPT"; option_code[39] = "NEW-ENVIRON"; option_code[40] = "TN3270E"; option_code[42] = "CHARSET"; option_code[44] = "COM-PORT-OPTION"; option_code[47] = "KERMIT"; option_code[250] = "SB"; option_code[240] = "SE"; option_code[251] = "WILL"; option_code[252] = "WONT"; option_code[253] = "DO"; option_code[254] = "DONT"; option_code[255] = "IAC"; if (buf[1] == DO && buf[2] == CMD_WINDOW_SIZE) { unsigned char tmp1[10] = { IAC, WILL, CMD_WINDOW_SIZE }; if (send(sock, tmp1, 3, 0) < 0) exit(1); unsigned char tmp2[10] = { IAC, SB, CMD_WINDOW_SIZE, 0, 80, 0, 24, IAC, SE }; if (send(sock, tmp2, 9, 0) < 0) exit(1); return; } for (i = 1; i < len; i++) { if (buf[i] == DO) { buf[i] = WONT; } else if (buf[i] == WILL) { buf[i] = DO; } } if (send(sock, buf, len, 0) < 0) exit(1); } static void terminal_set(void) { // save terminal configuration tcgetattr(STDIN_FILENO, &tin); static struct termios tlocal; memcpy(&tlocal, &tin, sizeof(tin)); // The file descriptor which has to be turned to raw mode is the standard // input of the parent process cfmakeraw(&tlocal); tcsetattr(STDIN_FILENO, TCSANOW, &tlocal); } static void terminal_reset(void) { // restore terminal upon exit tcsetattr(STDIN_FILENO, TCSANOW, &tin); } void connect_to_server(int sock, int port, char* address) { struct sockaddr_in server; server.sin_addr.s_addr = inet_addr(address); server.sin_family = AF_INET; server.sin_port = htons(port); //Connect to remote server if (connect(sock, (SA *) &server, sizeof(server)) < 0) { perror("connect failed. Error\n"); exit(1); } }
