#define NCCS 19
        struct termios {
                tcflag_t c_iflag;		/* input mode flags */
	        tcflag_t c_oflag;		/* output mode flags */
	        tcflag_t c_cflag;		/* control mode flags */
	        tcflag_t c_lflag;		/* local mode flags */
	        cc_t c_line;			/* line discipline */
	        cc_t c_cc[NCCS];		/* control characters */
        };
      ======
        #include <sys/types.h>
        #include <sys/stat.h>
        #include <fcntl.h>
        #include <termios.h>
        #include <stdio.h>

        /* baudrate settings are defined in <asm/termbits.h>, which is
        included by <termios.h> */
        #define BAUDRATE B38400            
        /* change this definition for the correct port */
        #define MODEMDEVICE "/dev/ttyS1"
        #define _POSIX_SOURCE 1 /* POSIX compliant source */

        #define FALSE 0
        #define TRUE 1

        volatile int STOP=FALSE; 

        main()
        {
          int fd,c, res;
          struct termios oldtio,newtio;
          char buf[255];
        /* 
          Open modem device for reading and writing and not as controlling tty
          because we don't want to get killed if linenoise sends CTRL-C.
        */
         fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY ); 
         if (fd <0) {perror(MODEMDEVICE); exit(-1); }
        
         tcgetattr(fd,&oldtio); /* save current serial port settings */
         bzero(&newtio, sizeof(newtio)); /* clear struct for new port settings */
        
        /* 
          BAUDRATE: Set bps rate. You could also use cfsetispeed and cfsetospeed.
          CRTSCTS : output hardware flow control (only used if the cable has
                    all necessary lines. See sect. 7 of Serial-HOWTO)
          CS8     : 8n1 (8bit,no parity,1 stopbit)
          CLOCAL  : local connection, no modem contol
          CREAD   : enable receiving characters
        */
         newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
         
        /*
          IGNPAR  : ignore bytes with parity errors
          ICRNL   : map CR to NL (otherwise a CR input on the other computer
                    will not terminate input)
          otherwise make device raw (no other input processing)
        */
         newtio.c_iflag = IGNPAR | ICRNL;
         
        /*
         Raw output.
        */
         newtio.c_oflag = 0;
         
        /*
          ICANON  : enable canonical input
          disable all echo functionality, and don't send signals to calling program
        */
         newtio.c_lflag = ICANON;
         
        /* 
          initialize all control characters 
          default values can be found in /usr/include/termios.h, and are given
          in the comments, but we don't need them here
        */
         newtio.c_cc[VINTR]    = 0;     /* Ctrl-c */ 
         newtio.c_cc[VQUIT]    = 0;     /* Ctrl-\ */
         newtio.c_cc[VERASE]   = 0;     /* del */
         newtio.c_cc[VKILL]    = 0;     /* @ */
         newtio.c_cc[VEOF]     = 4;     /* Ctrl-d */
         newtio.c_cc[VTIME]    = 0;     /* inter-character timer unused */
         newtio.c_cc[VMIN]     = 1;     /* blocking read until 1 character arrives */
         newtio.c_cc[VSWTC]    = 0;     /* '\0' */
         newtio.c_cc[VSTART]   = 0;     /* Ctrl-q */ 
         newtio.c_cc[VSTOP]    = 0;     /* Ctrl-s */
         newtio.c_cc[VSUSP]    = 0;     /* Ctrl-z */
         newtio.c_cc[VEOL]     = 0;     /* '\0' */
         newtio.c_cc[VREPRINT] = 0;     /* Ctrl-r */
         newtio.c_cc[VDISCARD] = 0;     /* Ctrl-u */
         newtio.c_cc[VWERASE]  = 0;     /* Ctrl-w */
         newtio.c_cc[VLNEXT]   = 0;     /* Ctrl-v */
         newtio.c_cc[VEOL2]    = 0;     /* '\0' */
        
        /* 
          now clean the modem line and activate the settings for the port
        */
         tcflush(fd, TCIFLUSH);
         tcsetattr(fd,TCSANOW,&newtio);
        
        /*
          terminal settings done, now handle input
          In this example, inputting a 'z' at the beginning of a line will 
          exit the program.
        */
         while (STOP==FALSE) {     /* loop until we have a terminating condition */
         /* read blocks program execution until a line terminating character is 
            input, even if more than 255 chars are input. If the number
            of characters read is smaller than the number of chars available,
            subsequent reads will return the remaining chars. res will be set
            to the actual number of characters actually read */
            res = read(fd,buf,255); 
            buf[res]=0;             /* set end of string, so we can printf */
            printf(":%s:%d\n", buf, res);
            if (buf[0]=='z') STOP=TRUE;
         }
         /* restore the old port settings */
         tcsetattr(fd,TCSANOW,&oldtio);
        }

      ======
      #include <sys/types.h>
      #include <sys/stat.h>
      #include <fcntl.h>
      #include <termios.h>
      #include <stdio.h>
              #define BAUDRATE B38400
      #define MODEMDEVICE "/dev/ttyS1"
      #define _POSIX_SOURCE 1 /* POSIX compliant source */
      #define FALSE 0
      #define TRUE 1
        
      volatile int STOP=FALSE; 
       
      main()
      {
        int fd,c, res;
        struct termios oldtio,newtio;
        char buf[255];
        
        fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY ); 
        if (fd <0) {perror(MODEMDEVICE); exit(-1); }
        
        tcgetattr(fd,&oldtio); /* save current port settings */
        
        bzero(&newtio, sizeof(newtio));
        newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
        newtio.c_iflag = IGNPAR;
        newtio.c_oflag = 0;
        
        /* set input mode (non-canonical, no echo,...) */
        newtio.c_lflag = 0;
         
        newtio.c_cc[VTIME]    = 0;   /* inter-character timer unused */
        newtio.c_cc[VMIN]     = 5;   /* blocking read until 5 chars received */
        
        tcflush(fd, TCIFLUSH);
        tcsetattr(fd,TCSANOW,&newtio);
        
        
        while (STOP==FALSE) {       /* loop for input */
          res = read(fd,buf,255);   /* returns after 5 chars have been input */
          buf[res]=0;               /* so we can printf... */
          printf(":%s:%d\n", buf, res);
          if (buf[0]=='z') STOP=TRUE;
        }
        tcsetattr(fd,TCSANOW,&oldtio);
======
      #include <termios.h>
      #include <stdio.h>
      #include <unistd.h>
      #include <fcntl.h>
      #include <sys/signal.h>
      #include <sys/types.h>
              #define BAUDRATE B38400
      #define MODEMDEVICE "/dev/ttyS1"
      #define _POSIX_SOURCE 1 /* POSIX compliant source */
      #define FALSE 0
      #define TRUE 1
        
      volatile int STOP=FALSE; 
        
      void signal_handler_IO (int status);   /* definition of signal handler */
      int wait_flag=TRUE;                    /* TRUE while no signal received */
        
      main()
      {
        int fd,c, res;
        struct termios oldtio,newtio;
        struct sigaction saio;           /* definition of signal action */
        char buf[255];
        
        /* open the device to be non-blocking (read will return immediatly) */
        fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY | O_NONBLOCK);
        if (fd <0) {perror(MODEMDEVICE); exit(-1); }
        
        /* install the signal handler before making the device asynchronous */
        saio.sa_handler = signal_handler_IO;
        saio.sa_mask = 0;
        saio.sa_flags = 0;
        saio.sa_restorer = NULL;
        sigaction(SIGIO,&saio,NULL);
          
        /* allow the process to receive SIGIO */
        fcntl(fd, F_SETOWN, getpid());
        /* Make the file descriptor asynchronous (the manual page says only 
           O_APPEND and O_NONBLOCK, will work with F_SETFL...) */
        fcntl(fd, F_SETFL, FASYNC);
        
        tcgetattr(fd,&oldtio); /* save current port settings */
        /* set new port settings for canonical input processing */
        newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
        newtio.c_iflag = IGNPAR | ICRNL;
        newtio.c_oflag = 0;
        newtio.c_lflag = ICANON;
        newtio.c_cc[VMIN]=1;
        newtio.c_cc[VTIME]=0;
        tcflush(fd, TCIFLUSH);
        tcsetattr(fd,TCSANOW,&newtio);
         
        /* loop while waiting for input. normally we would do something
           useful here */ 
        while (STOP==FALSE) {
          printf(".\n");usleep(100000);
          /* after receiving SIGIO, wait_flag = FALSE, input is available
             and can be read */
          if (wait_flag==FALSE) { 
            res = read(fd,buf,255);
            buf[res]=0;
            printf(":%s:%d\n", buf, res);
            if (res==1) STOP=TRUE; /* stop loop if only a CR was input */
            wait_flag = TRUE;      /* wait for new input */
          }
        }
        /* restore old port settings */
        tcsetattr(fd,TCSANOW,&oldtio);
      }
        
      /***************************************************************************
      * signal handler. sets wait_flag to FALSE, to indicate above loop that     *
      * characters have been received.                                           *
      ***************************************************************************/
        
      void signal_handler_IO (int status)
      {
        printf("received SIGIO signal.\n");
        wait_flag = FALSE;
      }
    
======
      #include <sys/time.h>
      #include <sys/types.h>
      #include <unistd.h>
              main()
      {
        int    fd1, fd2;  /* input sources 1 and 2 */
        fd_set readfs;    /* file descriptor set */
        int    maxfd;     /* maximum file desciptor used */
        int    loop=1;    /* loop while TRUE */ 
        
        /* open_input_source opens a device, sets the port correctly, and
           returns a file descriptor */
        fd1 = open_input_source("/dev/ttyS1");   /* COM2 */
        if (fd1<0) exit(0);
        fd2 = open_input_source("/dev/ttyS2");   /* COM3 */
        if (fd2<0) exit(0);
        maxfd = MAX (fd1, fd2)+1;  /* maximum bit entry (fd) to test */
        
        /* loop for input */
        while (loop) {
          FD_SET(fd1, &readfs);  /* set testing for source 1 */
          FD_SET(fd2, &readfs);  /* set testing for source 2 */
          /* block until input becomes available */
          select(maxfd, &readfs, NULL, NULL, NULL);
          if (FD_ISSET(fd1))         /* input from source 1 available */
            handle_input_from_source1();
          if (FD_ISSET(fd2))         /* input from source 2 available */
            handle_input_from_source2();
        }
      }   
    
======
        int res;
        struct timeval Timeout;

        /* set timeout value within input loop */
        Timeout.tv_usec = 0;  /* milliseconds */
        Timeout.tv_sec  = 1;  /* seconds */
        res = select(maxfd, &readfs, NULL, NULL, &Timeout);
        if (res==0)
        /* number of file descriptors with input = 0, timeout occurred. */ 
      
======

======

======