Programming

#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<termios.h>
#include<string.h>
#include<errno.h>
#include<sys/types.h>
#include<sys/select.h>
#include<string.h>
#include<sys/time.h>

void *thread_function(void *arg);
char quit='\0';/* this tends to terminate the read thread*/




      int open_port(void)
      {
      int fd;
      fd=open("dev/ttyS1",O_RDWR | O_NOCTTY | O_NDELAY);

      if(fd==-1)
      {
      fprintf(stderr,"open_port : unable to open /dev/ttyS1 -%s\n",strerror(errno));
      }
      return(fd);
      }




      
 int init_modem(int fd)   /* I - Serial port file */
    {

            char buffer[255];  /* Input buffer */
	    int  nbytes;       /* Number of bytes read */
            int  tries;        /* Number of tries so far */

            for (tries = 0; tries < 3; tries ++)
	    {
                    /* send an AT command followed by a CR */
                    if (write(fd, "AT\r", 3) < 3)
	             continue;
		    sleep(1);
		    nbytes=read(fd,&buffer,sizeof(buffer)-1);
		    if(nbytes<=0)
			    return 0;
		    else
		    {
			    buffer[nbytes]='\0';
			    printf("%s\n",buffer);
		    }

		   

		    write(fd,"AT+CREG?\r",9);
		    nbytes=0;
		    sleep(1);
		    nbytes=read(fd,&buffer,sizeof(buffer)-1);
		    buffer[nbytes]='\0';
		    printf("%s\n",buffer);
		    return 1;
	    }
	    return 0;
    }

	 
int  main()
{


      int mainfd=0;
      int res,iout;
      struct termios options;
      pthread_t a_thread;
      void *thread_result;
      char msg[256];


      mainfd=open_port(); 
      fcntl(mainfd,F_SETFL,FNDELAY);
      tcgetattr(mainfd,&options);
      cfsetispeed(&options,B9600);
      cfsetospeed(&options,B9600);



      /*modem setting */
      options.c_cflag |=(CLOCAL | CREAD);
      options.c_oflag &= ~OPOST;
      options.c_cflag &= ~PARENB;
      options.c_cflag &= ~CSTOPB;
      options.c_cflag |= ~CSIZE;
      options.c_cflag |= CS8;
      options.c_cflag &= ~CRTSCTS;

      options.c_lflag &=~(ICANON | ECHO | ISIG);
      tcsetattr(mainfd,TCSANOW,&options);


     if(init_modem(mainfd)==0)
       {
         printf("modem bad, run again\n");
         exit(0);
       }

     
     printf("every thing working continue\n");
     res=pthread_create(&a_thread,NULL,thread_function,(void*)mainfd);
     if(res!=0)
     {
	     perror("thread creation failed\n");
	     exit(EXIT_FAILURE);
     }
     printf("enter commands or message and type q to exit\n");

     while(1)
     {
	     fflush(stdin);
	     printf("#");
	     gets(msg);
	     if(strcmp(msg,"q")==0 || strcmp(msg,"Q")==0)
	     {
		     quit='q';
		     break;
	     }
	     
	    iout= write(mainfd,&msg,strlen(msg));
	     if (iout < 0)
		     {
			     printf("write error %d %s\n", errno, strerror(errno));
		     }
	     else
	     {
		     printf("wrote %d chars:", iout);
	     }
	     sleep(4);/*time for processing*/
     
     }

      res=pthread_join(a_thread,&thread_result);
      if(res!=0)
      {
	      perror("thread join failed\n");
	      exit(EXIT_FAILURE);
      }
      printf("thread joined it returned%s\n",(char*)thread_result);
      printf("application ended\n");
}



void *thread_function(void *arg)
{


	int fd;
	char buffer2[256];
	int n,in;
	int max_fd;
	fd_set input;
	struct timeval timeout;

	/*initilize the input set*/
	fd=*((int*)arg);
	FD_ZERO(&input);
	FD_SET(fd,&input);
	max_fd=fd+1;

	timeout.tv_sec=3;
	timeout.tv_usec=0;

	/*looping with select*/
	while(1)
	{
		n=select(max_fd,&input,NULL,NULL,&timeout);/*this wait for 3 sec for any input in the input bufferand then it just go down to check for status of quit and then again comes back*/
		if(n<0)
			perror("select failed");
		else if(n==0)
		{}
		else
		{
			/*we have input*/
			if(FD_ISSET(fd,&input))
			{
				/*we have something in the input buffer waiting to be read*/
				in=read(fd,&buffer2,255)
				if(in<0)
				{
					printf("read error %d %s\n", errno, strerror(errno));
				}

				else
				{
					buffer2[in] = '\0';
					printf("%s\n",buffer2);
				}	
			}
		}
		if(quit=='q')
			break;
	}
	pthread_exit("reading thread also exiting\n");
}