Thread: receiving in a value and i am storing it in a buff. explain me logic here

What is this code supposed to do and how does it not work? Post the smallest and simplest compilable program that demonstrates the problem.

Code:

        while(1)    {
        ret = (PortRecvs(0,buff,sizeof(buff)-1,1000)<0);     // r=registration is the command used in recv         
        if(ret<0)       
        { printf("j = %d",j);
           DelayMs(1000);
         if(j == 12)         
         { if(PortSends(0,DeviceId,sizeof(DeviceId))!=0)// working fine untill here 
              memset(buff,0,sizeof(buff));
              while(1)
         {
             ret = (PortRecvs(0,buff,sizeof(buff)-1,1000)<0);   // receiving number     
             if(ret<0)       {printf("Receive Data:\n%d\n",buff);
         }
             for(i=48;i<60;i++)
         {
                      
              printf("%c",buff[i]);
              DelayMs(500);
           }
              im=0;
              i=48;
              while(im<12)                                                
         {
              m2[im]=buff[i]; 
              i++;
              im++;
         }
             ScrCls();
             printf("Reg no:\n %s",m2);// reg no is not constant keeps on fluctuating
             DelayMs(2000);
             break;
        }
        }
             if(PortSends(0,"Registration Completed",22)!=0)    
             while(1)
       {
              ret = (PortRecvs(0,buff,sizeof(buff)-1,1000)<0);             
              if(ret<0)       
       { 
               ScrCls();
               printf("Receive Fail..");
                  
         }
              else
       {
                 ScrCls();
            for(i=160;i<170;i++)
              {
                       
                printf("%c",buff[i]);
                DelayMs(500);
             }
                 printf("Receive Close Command :\n%s\n",buff);
                 DelayMs(3000);
                  
               }
                  break;
             }
                 im=0;
                 i=160;
                 while(im<5)                                        
             {
                    m1[im]=buff[i];
                      i++;
                     im++;
               }
                    im=0;
                    x=0;
                  while(m1[im]==command2[im])
             {
                   im++;
                   x++;
             }                                                     
                  ScrCls();
                  printf(" x = %d \n",x);
                  DelayMs(500);
                  while(x==1 || x==5)
           {
                  ScrCls();
                  printf("Close command....");
                  DelayMs(500);
                    break;
            }    
         }
                  PortClose(0);

I want to register my device using serial port communication between "visual studio c -pos machine- Java fX".
So ,
1.receive :i need to get registration command from Java fx
2.send: I am comparing length , if it is 12 then i am sending device id of length 8
3.receive : now i need to receive registration number from the java fx .i.e., ex/- 12345678:214.
4.send: if i get registration number then i am comparing , if length = 12 then i am sending registration completed of length 22.
5.receive : now , if length =22 then he validates and sends close command to me.

issue: in step 3 , registration number is not constant , it keeps on overlapping or sometimes i am not getting the data.

I searched many blogs and did my attempt, but i am not getting what the exact problem is? please explain me.

why Java fx is used for offline application?