Tiny Serial Console COM

Tiny Serial Code :

/*
 * Building: cc -o com com.c
 * Usage   : ./com /dev/device [speed]
 * Example : ./com /dev/ttyS0 [115200]
 * Keys    : Ctrl-A - exit, Ctrl-X - display control lines status
 * Darcs   : darcs get http://tinyserial.sf.net/
 * Homepage: http://tinyserial.sourceforge.net
 * Version : 2009-03-05
 *
 * Ivan Tikhonov, http://www.brokestream.com, [email protected]
 * Patches by Jim Kou, Henry Nestler, Jon Miner, Alan Horstmann
 *
 */


/* Copyright (C) 2007 Ivan Tikhonov

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Ivan Tikhonov, [email protected]

*/

#include <termios.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>

int transfer_byte(int from, int to, int is_control);

typedef struct {char *name; int flag; } speed_spec;


void print_status(int fd) {
	int status;
	unsigned int arg;
	status = ioctl(fd, TIOCMGET, &arg);
	fprintf(stderr, "[STATUS]: ");
	if(arg & TIOCM_RTS) fprintf(stderr, "RTS ");
	if(arg & TIOCM_CTS) fprintf(stderr, "CTS ");
	if(arg & TIOCM_DSR) fprintf(stderr, "DSR ");
	if(arg & TIOCM_CAR) fprintf(stderr, "DCD ");
	if(arg & TIOCM_DTR) fprintf(stderr, "DTR ");
	if(arg & TIOCM_RNG) fprintf(stderr, "RI ");
	fprintf(stderr, "\r\n");
}

int main(int argc, char *argv[])
{
	int comfd;
	struct termios oldtio, newtio;       //place for old and new port settings for serial port
	struct termios oldkey, newkey;       //place tor old and new port settings for keyboard teletype
	char *devicename = argv[1];
	int need_exit = 0;
	speed_spec speeds[] =
	{
		{"1200", B1200},
		{"2400", B2400},
		{"4800", B4800},
		{"9600", B9600},
		{"19200", B19200},
		{"38400", B38400},
		{"57600", B57600},
		{"115200", B115200},
		{NULL, 0}
	};
	int speed = B9600;

	if(argc < 2) {
		fprintf(stderr, "example: %s /dev/ttyS0 [115200]\n", argv[0]);
		exit(1);
	}

	comfd = open(devicename, O_RDWR | O_NOCTTY | O_NONBLOCK);
	if (comfd < 0)
	{
		perror(devicename);
		exit(-1);
	}

	if(argc > 2) {	
		speed_spec *s;
		for(s = speeds; s->name; s++) {
			if(strcmp(s->name, argv[2]) == 0) {
				speed = s->flag;
				fprintf(stderr, "setting speed %s\n", s->name);
				break;
			}
		}
	}

	fprintf(stderr, "C-a exit, C-x modem lines status\n");

	tcgetattr(STDIN_FILENO,&oldkey);
	newkey.c_cflag = B9600 | CRTSCTS | CS8 | CLOCAL | CREAD;
	newkey.c_iflag = IGNPAR;
	newkey.c_oflag = 0;
	newkey.c_lflag = 0;
	newkey.c_cc[VMIN]=1;
	newkey.c_cc[VTIME]=0;
	tcflush(STDIN_FILENO, TCIFLUSH);
	tcsetattr(STDIN_FILENO,TCSANOW,&newkey);


	tcgetattr(comfd,&oldtio); // save current port settings 
	newtio.c_cflag = speed | CS8 | CLOCAL | CREAD;
	newtio.c_iflag = IGNPAR;
	newtio.c_oflag = 0;
	newtio.c_lflag = 0;
	newtio.c_cc[VMIN]=1;
	newtio.c_cc[VTIME]=0;
	tcflush(comfd, TCIFLUSH);
	tcsetattr(comfd,TCSANOW,&newtio);

	print_status(comfd);

	while(!need_exit) {
		fd_set fds;
		int ret;
		
		FD_ZERO(&fds);
		FD_SET(STDIN_FILENO, &fds);
		FD_SET(comfd, &fds);


		ret = select(comfd+1, &fds, NULL, NULL, NULL);
		if(ret == -1) {
			perror("select");
		} else if (ret > 0) {
			if(FD_ISSET(STDIN_FILENO, &fds)) {
				need_exit = transfer_byte(STDIN_FILENO, comfd, 1);
			}
			if(FD_ISSET(comfd, &fds)) {
				need_exit = transfer_byte(comfd, STDIN_FILENO, 0);
			}
		}
	}

	tcsetattr(comfd,TCSANOW,&oldtio);
	tcsetattr(STDIN_FILENO,TCSANOW,&oldkey);
	close(comfd);

	return 0;
}


int transfer_byte(int from, int to, int is_control) {
	char c;
	int ret;
	do {
		ret = read(from, &c, 1);
	} while (ret < 0 && errno == EINTR);
	if(ret == 1) {
		if(is_control) {
			if(c == '\x01') { // C-a
				return -1;
			} else if(c == '\x18') { // C-x
				print_status(to);
				return 0;
			}
		}
		while(write(to, &c, 1) == -1) {
			if(errno!=EAGAIN && errno!=EINTR) { perror("write failed"); break; }
		}
	} else {
		fprintf(stderr, "\nnothing to read. probably port disconnected.\n");
		return -2;
	}
	return 0;
}

Save to com.c
Building: cc -o com com.c
Usage  : ./com /dev/device [speed]
Example : ./com /dev/ttyS0 [115200]
Keys  : Ctrl-A - exit, Ctrl-X - display control lines status
Sorce

Another Serial terminal : There is a teletype tool written by Clifford Wolf based on tinyserial which is much more advanced.

/*
 * Copyright (C) 2008 Clifford Wolf
 *
 * This program is based on Ivan Tikhonov's tinyserial project.
 * http://tinyserial.sourceforge.net
 *
 * ----------------------------------------------------------------------
 *
 * Usage: teletype device [speed] [escape-letter] [command(s)]
 *
 * Default speed is 9600 Baud.
 * Default escape letter is 'A'.
 *   
 * Control Key Kombos:
 *
 *   Ctrl-A A       Send a Ctrl-A over the line
 *   Ctrl-A B       Send a break over the line
 *   Ctrl-A P       Set the break period in deciseconds
 *   Ctrl-A 0       Send a a single zero byte over the line
 *   Ctrl-A H       Print help message (command overview)
 *   Ctrl-A R       Toggle RTS (Ready To Send) signal
 *   Ctrl-A D       Toggle DTR (Data Terminal Ready) signal
 *   Ctrl-A T       Toggle timestamp-mode and reset timer
 *   Ctrl-A L       Set slow send mode (N chars/sec, 0=unlimited)
 *   Ctrl-A N       Create network link to remote TCP/IP port
 *   Ctrl-A E       Toggle local terminal echo
 *   Ctrl-A C       Run a chat script (or any other command such as 'sx')
 *   Ctrl-A W       Wait one second (this is usefull for scripts)
 *   Ctrl-A U       Set baud rate (use with care!)
 *   Ctrl-A S       Print line status
 *   Ctrl-A \       Exit without serial reset
 *   Ctrl-A X       Exit with serial reset
 *
 *   Ctrl-A . [x]   Change escape key from Ctrl-A to Ctrl-[x]
 *
 * Commands are in the form of '-<Key><Argument>'. E.g.:
 * teletype /dev/tts 9600 -b -l10 -c'chat -f myscript.txt' -l0 -u115200 -c'sx datafile.bin' -x
 *
 * ----------------------------------------------------------------------
 *
 * Ivan Tikhonov, http://www.brokestream.com, [email protected]
 * Patches by Jim Kou ([email protected]) and Henry Nestler
 *
 * Copyright (C) 2007 Ivan Tikhonov
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 *
 * Ivan Tikhonov, [email protected]
 *
 */

#define _GNU_SOURCE

#include <termios.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <errno.h>

typedef struct { char *name; int flag; } speed_spec;

speed_spec speeds[] =
{
	{"1200", B1200},
	{"2400", B2400},
	{"4800", B4800},
	{"9600", B9600},
	{"19200", B19200},
	{"38400", B38400},
	{"57600", B57600},
	{"115200", B115200},
	{NULL, 0}
};

struct termios newtio;

char escape_letter = 'A';

int timestamp_mode = 0;
struct timeval timestamp_start;

int chat_ptmx = -1;
int chat_autoexit = 0;
int break_period = 0;

int skip_serial_reset = 0;
int slow_send = 0;
int local_echo = 0;
int comfd;

int net_fd;
struct sockaddr_in net_peer;
int net_active;

void print_status(int fd)
{
	unsigned int arg;
	ioctl(fd, TIOCMGET, &arg);
	fprintf(stderr, "[STATUS]:");
	if (arg & TIOCM_RTS) fprintf(stderr, " RTS");
	if (arg & TIOCM_CTS) fprintf(stderr, " CTS");
	if (arg & TIOCM_DSR) fprintf(stderr, " DSR");
	if (arg & TIOCM_CAR) fprintf(stderr, " DCD");
	if (arg & TIOCM_DTR) fprintf(stderr, " DTR");
	if (arg & TIOCM_RNG) fprintf(stderr, " RI");
	fprintf(stderr, "\r\n");
}

void print_help(int command_line_usage)
{
	fprintf(stderr, "\r\n");
	fprintf(stderr, "---------------------------------------------------------\r\n");
	fprintf(stderr, "\r\n");
	if (command_line_usage) {
		fprintf(stderr, "Usage: teletype device [speed] [escape-letter] [command(s)]\r\n");
		fprintf(stderr, "\r\n");
		fprintf(stderr, "Default speed is 9600 Baud.\r\n");
		fprintf(stderr, "Default escape letter is 'A'.\r\n");
		fprintf(stderr, "\r\n");
		fprintf(stderr, "Supported speed rates:\r\n");
		speed_spec *s;
		for (s = speeds; s->name; s++) {
			fprintf(stderr, "%s%s", s == speeds ? "  " : ", ", s->name);
		}
		fprintf(stderr, "\r\n\r\n");
	}
	fprintf(stderr, "Control Key Kombos:\r\n");
	fprintf(stderr, "\r\n");
	fprintf(stderr, "  Ctrl-%c A       Send a Ctrl-%c over the line\r\n", escape_letter, escape_letter);
	fprintf(stderr, "  Ctrl-%c B       Send a break over the line\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c P       Set the break period in deciseconds\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c 0       Send a a single zero byte over the line\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c H       Print help message (command overview)\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c R       Toggle RTS (Ready To Send) signal\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c D       Toggle DTR (Data Terminal Ready) signal\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c T       Toggle timestamp-mode and reset timer\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c L       Set slow send mode (N chars/sec, 0=unlimited)\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c N       Create network link to remote TCP/IP port\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c E       Toggle local terminal echo\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c C       Run a chat script (or any other command such as 'sx')\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c W       Wait one second (this is usefull for scripts)\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c U       Set baud rate (use with care!)\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c S       Print line status\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c \\       Exit without serial reset\r\n", escape_letter);
	fprintf(stderr, "  Ctrl-%c X       Exit with serial reset\r\n", escape_letter);
	fprintf(stderr, "\r\n");
	fprintf(stderr, "  Ctrl-%c . [x]   Change escape key from Ctrl-%c to Ctrl-[x]\r\n", escape_letter, escape_letter);
	fprintf(stderr, "\r\n");
	if (command_line_usage) {
		fprintf(stderr, "Commands are in the form of '-<Key><Argument>'. E.g.:\r\n");
		fprintf(stderr, "teletype /dev/tts 9600 -b -l10 -c'chat -f myscript.txt' -l0 -u115200 -c'sx datafile.bin' -x\r\n");
		fprintf(stderr, "\r\n");
	}
	fprintf(stderr, "---------------------------------------------------------\r\n");
	fprintf(stderr, "\r\n");
}

void chat_close()
{
	if (chat_ptmx != -1) {
		close(chat_ptmx);
		chat_ptmx = -1;
	}
}

void chat_open(const char *command_string)
{
	chat_close();

	fprintf(stderr, "** CONTROL TURNED OVER TO CHAT SCRIPT (Ctrl-C = Abort) **\r\n");

	chat_ptmx = posix_openpt(O_RDWR|O_NOCTTY);

	grantpt(chat_ptmx);
	unlockpt(chat_ptmx);

	if (!fork())
	{
		close(0);
		close(1);

		open(ptsname(chat_ptmx), O_RDWR);
		if (dup(0) < 0) {
			perror("dup in chat_open() failed");
			_exit(-1);
		}

		execl("/bin/sh", "sh", "-c", command_string, NULL);
		_exit(-1);
	}
}

float tv_diff(struct timeval *a, struct timeval *b)
{
	float diff = 0;
	if (a->tv_sec < b->tv_sec)
		diff = ((1000000 - a->tv_usec) + b->tv_usec) / 1000000.0 + (b->tv_sec - (a->tv_sec + 1));
	else
		diff = (b->tv_usec - a->tv_usec) / 1000000.0;
	return diff;
}

int user_input(int from, char *prompt, char *line, int n, char *argument)
{
	if (argument) {
		snprintf(line, n, "%s", argument);
		fprintf(stderr, "\r\n%s: %s\r\n", prompt, line);
		return 0;
	}

	char c;
	int i = strlen(line);

	fprintf(stderr, "\r\n%s: %s", prompt, line);

	while (1)
	{
		if (read(from, &c, 1) != 1)
			return 1;
		if (c == '\b' || c == 127) {
			if (i > 0) {
				fprintf(stderr, "\b \b");
				line[--i] = 0;
			}
		} else if (c == 21 /* NAK */) {
			while (i > 0) {
				fprintf(stderr, "\b \b");
				line[--i] = 0;
			}
		} else if (c == '\r' || c == '\n') {
			fprintf(stderr, "\r\n");
			return 0;
		} else if (c >= ' ' && i < n-1) {
			fputc(c, stderr);
			line[i++] = c;
			line[i] = 0;
		}
	}
}

int transfer_byte(int from, int to, int is_control, int command, char *argument)
{
	char c;
	static int got_escape = 0;
	char escape_c = escape_letter - 'A' + 1;
	if (command || read(from, &c, 1) == 1)
	{
		if (command || is_control) {
			if (command || got_escape) {
				if (command)
					c = command;
				got_escape = 0;
				if (c == 'b' || c == 'B') {
					if (break_period == 0) {
						tcsendbreak(to, 0);
					} else {
						ioctl(to, TCSBRKP, break_period);
					}
					return 0;
				}
				if (c == 'p' || c == 'P') {
					static char periodstring[4096] = "";

					if (user_input(from, "Enter break period in deciseconds (0=default)", periodstring, 4096, argument))
						goto read_error;

					break_period = atoi(periodstring);

					return 0;
				}
				if (c == '0') {
					c = 0;
					goto send_byte;
				}
				if (c == 'h' || c == 'H') {
					print_help(0);
					return 0;
				}
				if (c == 'r' || c == 'R') {
					unsigned int arg;
					ioctl(to, TIOCMGET, &arg);
					arg ^= TIOCM_RTS;
					ioctl(to, TIOCMSET, &arg);
					return 0;
				}
				if (c == 'd' || c == 'D') {
					unsigned int arg;
					ioctl(to, TIOCMGET, &arg);
					arg ^= TIOCM_DTR;
					ioctl(to, TIOCMSET, &arg);
					return 0;
				}
				if (c == 't' || c == 'T') {
					gettimeofday(&timestamp_start, NULL);
					timestamp_mode = !timestamp_mode;
					return 0;
				}
				if (c == 'l' || c == 'L') {
					static char ratestring[4096] = "";

					if (user_input(from, "Enter rate in chars/second (0=unlimited)", ratestring, 4096, argument))
						goto read_error;

					slow_send = atoi(ratestring);

					return 0;
				}
				if (c == 'n' || c == 'N') {
					static char connstring[4096] = "";

					if (user_input(from, "Enter remote port (IP-ADDR:PORT)", connstring, 4096, argument))
						goto read_error;

					char *ips = strtok(connstring, ":");
					char *ports = strtok(NULL, "");

					if (net_active) {
						close(net_fd);
						net_active = 0;
					}

					if (ips && ports) {
						bzero(&net_peer, sizeof(net_peer));
						net_peer.sin_family = AF_INET;
						net_peer.sin_addr.s_addr = inet_addr(ips);
						net_peer.sin_port = htons(atoi(ports));
						net_fd = socket(PF_INET, SOCK_STREAM, 0);
						connect(net_fd, (struct sockaddr*)&net_peer, sizeof(net_peer));
						net_active = 1;
					}

					return 0;
				}
				if (c == 'e' || c == 'E') {
					local_echo = !local_echo;
					return 0;
				}
				if (c == 's' || c == 'S') {
					print_status(to);
					return 0;
				}
				if (c == 'c' || c == 'C') {
					static char command[4096] = "";

					if (user_input(from, "Enter chat script command", command, 4096, argument))
						goto read_error;

					if (command[0])
						chat_open(command);

					return 0;
				}
				if (c == 'w' || c == 'W') {
					sleep(1);
					return 0;
				}
				if (c == 'u' || c == 'U') {
					static char baud_rate[4096] = "";

					if (user_input(from, "Enter new baud rate", baud_rate, 4096, argument))
						goto read_error;

					speed_spec *s;
					for (s = speeds; s->name; s++) {
						if(strcmp(s->name, baud_rate) == 0) {
							newtio.c_cflag = s->flag | CS8 | CREAD;
							tcflush(to, TCIFLUSH);
							tcsetattr(to, TCSANOW, &newtio);
							break;
						}
					}

					return 0;
				}
				if (c == '\\') {
					fprintf(stderr, "\r\nBye (without reset).\r\n");
					skip_serial_reset = 1;
					return -1;
				}
				if (c == 'x' || c == 'X') {
					fprintf(stderr, "\r\nBye.\r\n");
					return -1;
				}
				if (c == '.') {
					fprintf(stderr, "\r\nType new escape letter: ");
					if (read(from, &c, 1) != 1)
						goto read_error;
					if (c >= 'a' && c <= 'z')
						c -= 'a' - 'A';
					if (c >= 'A' && c <= 'Z') {
						escape_letter = c;
						fprintf(stderr, "%c\r\nType [Ctrl-%c H] for help\r\n", escape_letter, escape_letter);
					} else {
						fprintf(stderr, "%c\r\nThe character you typed is not a letter!\r\n", c);
					}
					return 0;
				}
				if (write(to, &escape_c, 1) != 1) {
					perror("write failed");
					return -1;
				}
				if (c == 'a' || c == 'A')
					return 0;
			}
			if (c == escape_c) {
				got_escape = 1;
				return 0;
			}
		}

		if (!is_control && timestamp_mode)
		{
			static int got_nl_cr = 0;

			if (c == '\n' || c == '\r') {
				got_nl_cr = 1;
			} else
			if (got_nl_cr) {
				struct timeval tv;
				gettimeofday(&tv, NULL);
				fprintf(stdout, "<%7.3fs> ", tv_diff(&timestamp_start, &tv));
				fflush(stdout);
				got_nl_cr = 0;
			}
		}

send_byte:
		if (slow_send && to != STDOUT_FILENO) {
			usleep(1000000 / slow_send);
		}
		if (to == STDOUT_FILENO && chat_ptmx != -1) {
			if (write(chat_ptmx, &c, 1) != 1)
				perror("Single char write to chat_ptmx failed");
		}
		if (to == STDOUT_FILENO && net_active) {
			if (write(net_fd, &c, 1) != 1)
				perror("Single char write to net_fd failed");
		}
		if (to == comfd && local_echo) {
			if (write(STDOUT_FILENO, &c, 1) != 1)
				perror("Single char write to STDOUT_FILENO failed");
			if (c == '\r') {
				if (write(STDOUT_FILENO, "\n", 1) != 1)
					perror("Single char write to STDOUT_FILENO failed");
			}
		}
		if (write(to, &c, 1) != 1) {
			perror("write failed");
			return -2;
		}
	}
	else
	{
read_error:
		if (from == chat_ptmx && chat_ptmx != -1) {
			chat_close();
			int status;
			if (wait(&status) >= 0 && WEXITSTATUS(status) != 0) {
				fprintf(stderr, "\r\n** CHAT SCRIPT RETURNED ERROR CODE %d! **\r\n", WEXITSTATUS(status));
				return -1;
			}
			fprintf(stderr, "\r\n** END OF CHAT SCRIPT **\r\n");
			return chat_autoexit;
		}
		fprintf(stderr, "nothing to read. probably port disconnected.\n");
		return -2;
	}
	return 0;
}

int main(int argc, char *argv[])
{
	struct termios oldtio;
	struct termios oldkey_stdin, oldkey_stdout, newkey;
	char *devicename = argv[1];
	int need_exit = 0;
	int speed = B9600;

	if (argc < 2)
	{
		print_help(1);
		exit(1);
	}

	comfd = open(devicename, O_RDWR | O_NOCTTY | O_NONBLOCK);
	if (comfd < 0)
	{
		perror(devicename);
		exit(-1);
	}

	while (argc > 2)
	{	
		speed_spec *s;
		for (s = speeds; s->name; s++) {
			if(strcmp(s->name, argv[2]) == 0) {
				speed = s->flag;
				break;
			}
		}
		if (s->name) {
			argc--; argv++;
			continue;
		}

		if (argv[2][0] >= 'A' && argv[2][0] <= 'Z' && !argv[2][1]) {
			escape_letter = argv[2][0];
			argc--; argv++;
			continue;
		}

		if (argv[2][0] >= 'a' && argv[2][0] <= 'z' && !argv[2][1]) {
			escape_letter = argv[2][0] - ('a' - 'A');
			argc--; argv++;
			continue;
		}

		// if ((argv[2][0] < '0' || argv[2][0] > '9') && argv[2][1]) {
		// 	chat_open(argv[2]);
		// 	chat_autoexit = 1;
		// 	argc--; argv++;
		// 	continue;
		// }

		if (argv[2][0] == '-')
			break;

		print_help(1);
		exit(1);
	}

	tcgetattr(STDIN_FILENO, &oldkey_stdin);
	tcgetattr(STDOUT_FILENO, &oldkey_stdout);
	memset(&newkey, 0, sizeof(newkey));
	newkey.c_cflag = B9600 | CRTSCTS | CS8 | CLOCAL | CREAD;
	newkey.c_iflag = IGNPAR;
	newkey.c_oflag = 0;
	newkey.c_lflag = 0;
	newkey.c_cc[VMIN]=1;
	newkey.c_cc[VTIME]=0;
	tcflush(STDIN_FILENO, TCIFLUSH);
	tcflush(STDOUT_FILENO, TCIFLUSH);
	tcsetattr(STDIN_FILENO, TCSANOW, &newkey);
	tcsetattr(STDOUT_FILENO, TCSANOW, &newkey);

	tcgetattr(comfd, &oldtio);
	newtio.c_cflag = speed | CS8 | CREAD;
	newtio.c_iflag = IGNPAR;
	newtio.c_oflag = 0;
	newtio.c_lflag = 0;
	newtio.c_cc[VMIN]=1;
	newtio.c_cc[VTIME]=0;
	tcflush(comfd, TCIFLUSH);
	tcsetattr(comfd, TCSANOW, &newtio);

	if (!chat_autoexit) {
		fprintf(stderr, "Type [Ctrl-%c H] for help\r\n", escape_letter);
		print_status(comfd);
	}

	while (!need_exit)
	{
		fd_set fds;
		int max_fd = 0;
		int ret;
		
		FD_ZERO(&fds);

		if (chat_ptmx != -1) {
			FD_SET(chat_ptmx, &fds);
			if (chat_ptmx >= max_fd)
				max_fd = chat_ptmx+1;
		}

		FD_SET(STDIN_FILENO, &fds);
		if (STDIN_FILENO >= max_fd)
			max_fd = STDIN_FILENO+1;

		FD_SET(comfd, &fds);
		if (comfd >= max_fd)
			max_fd = comfd+1;

		if (net_active) {
			FD_SET(net_fd, &fds);
			if (net_fd >= max_fd)
				max_fd = net_fd+1;
		}

		if (argc > 2 && chat_ptmx == -1) {
			struct timeval timeout = { 0, 100000 };
			ret = select(max_fd, &fds, NULL, NULL, &timeout);
		} else {
			ret = select(max_fd, &fds, NULL, NULL, NULL);
		}
		if (ret == -1) {
			perror("select");
			need_exit = -2;
		} else if (ret > 0) {
			if (FD_ISSET(comfd, &fds)) {
				need_exit = transfer_byte(comfd, STDOUT_FILENO, 0, 0, NULL);
			} else if (FD_ISSET(STDIN_FILENO, &fds)) {
				if (argc > 2) {
					unsigned char ch;
					if (read(STDIN_FILENO, &ch, 1) == 1 && ch == 3) {
						fprintf(stderr, "\r\n** COMMANDS ABORT **\r\n");
						need_exit = -3;
					}
				} else if (chat_ptmx != -1) {
					unsigned char ch;
					if (read(STDIN_FILENO, &ch, 1) == 1 && ch == 3) {
						fprintf(stderr, "\r\n** CHAT SCRIPT ABORT **\r\n");
						chat_close();
						if (chat_autoexit) {
							fprintf(stderr, "Type [Ctrl-%c H] for help\r\n", escape_letter);
							chat_autoexit = 0;
						}
					}
				} else
					need_exit = transfer_byte(STDIN_FILENO, comfd, 1, 0, NULL);
			} else if (chat_ptmx != -1 && FD_ISSET(chat_ptmx, &fds)) {
				need_exit = transfer_byte(chat_ptmx, comfd, 0, 0, NULL);
			} else if (net_active && FD_ISSET(net_fd, &fds)) {
				need_exit = transfer_byte(net_fd, comfd, 0, 0, NULL);
			}
		} else if (argc > 2 && chat_ptmx == -1) {
			if (argv[2][0] == '-' && argv[2][1]) {
				fprintf(stderr, "\r\n** COMMAND: %s **\r\n", &argv[2][1]);
				need_exit = transfer_byte(STDIN_FILENO, comfd, 1, argv[2][1], &argv[2][2]);
				argc--; argv++;
			} else {
				fprintf(stderr, "\r\n** COMMANDS SYNTAX ERROR **\r\n");
				need_exit = 1;
			}
		}
	}

	tcsetattr(STDIN_FILENO, TCSANOW, &oldkey_stdin);
	tcsetattr(STDOUT_FILENO, TCSANOW, &oldkey_stdout);
	if (!skip_serial_reset)
		tcsetattr(comfd, TCSANOW, &oldtio);
	close(comfd);

	return need_exit < 0 ? -need_exit : 0;
}

Source
Another easy to use include GUI program:Cutecom