weird change from char to int , serial port communication c - c

Question

I am working an a serial communication project where two applications server and client will send to each other messages.
For example client send a string command server receives this and after processing response with a value. One example of that is : client AT+REG1 server value.
If client sends the message AT+REG1=value then the server must inform his system that the value of current register1 which client needs has changed.
In order to achieve this I keep a stack where at the beginning of the program I am pushing into stack a default value for register1 and if server detect this message AT+REG1= pops the old value and push the new into stack.
Currently if client sends the message AT+REG1, server must response with the new value and not with the old one that I push it by default in the beginning. All the stuff in pop push and generally at stack operations are going right.
My problem is, when I start with AT+REG1, client receives the default value but when I start with AT+REG1=5 (server must change the value from the stack and replace it with the new "5") I am not getting any response. At this point I have to mention that in terminal I am seeing the changes in the stack (with printf for example at AT+REG1=5 , he pops the old and push the new) but I cannot have the result.
The problem that I noticed when trying to print the value that pops out from stack terminal says that it is of type int DESPITE that am not using or creating integers, all the values are in char form.
SERVER.C
//data structures
typedef enum operation{
insert,
read_reg,
info
}Operation;
typedef struct request{
Operation operation;
char old_value1[SIZE];
char old_value2[SIZE];
int flag; //flag to know which register is
int counter1;
int counter2;
}Request;
Request c1;
Request c2;
//Prototype Functions
Request *parse_request(char *buffer);
void process_request(int fd);
int isEmpty(char *stack);
int isFull(char *stack);
void push(char num,char *stack);
char pop(char *stack);
char *stack1,*stack2;
int top1=-1,top2=-1;
char t1,t2;
int main(int argc , char * argv[]){
int fd; //file descriptor of the port
char *port; // port name
struct termios tty; //connection manager
stack1=(char*)malloc(STACK_SIZE*sizeof(char));
stack2=(char*)malloc(STACK_SIZE*sizeof(char));
if(argc < 1){
printf("You have to enter a specific tty file to open\n");
exit(1);
}
//Opening port .
port =argv[1];
fd=open(port,O_RDWR|O_NOCTTY| O_NONBLOCK);
if(fd==-1){
perror(port);
exit(1);
}
printf("[+] port opened succesfully!\n");
if(tcgetattr(fd,&tty)!=0){
printf("tcgetattr : %s \n",strerror(errno));
}
//BAUD RATE SETTINGS (read and write speed)
cfsetospeed(&tty,B115200);
cfsetispeed(&tty,B115200);
cfmakeraw(&tty);
// Settings for control modes
tty.c_cflag &= ~PARENB; // Clear the parity bit for the serial communication
tty.c_cflag &= ~CSTOPB; // Using only one stop bit in this communication
tty.c_cflag |= CS8; // Set 8 bits per byte in transmittion
tty.c_cflag &= ~CRTSCTS; // Disable the RTS/CTS flow control
tty.c_cflag |= CREAD | CLOCAL; // Setting clocal up ("1") .Usefull for reading data
tty.c_lflag &= ~ICANON; // Setting on the non-canonical mode
tty.c_lflag &= ~ISIG; // Disable the INTR - QUIT - SUSP characters
tty.c_iflag &= ~IGNPAR;
//Blocking read operation and setting maximum timeout 1 second
tty.c_cc[VTIME]=1;
tty.c_cc[VMIN] =0;
//Setting the options
tcsetattr(fd,TCSANOW,&tty);
//setting first values for each register!
push('0',stack1);
push('1',stack2);
c1.counter1=0;
c2.counter2=0;
printf("[+] Connection starting !\n");
while(1){
process_request(fd);
}
}
Request *parse_request(char *buffer){
char *token=NULL;
char *take[3];
int i=0,num;
Request *rep=NULL;
if(!buffer)
return NULL;
rep=(Request*)malloc(sizeof(Request));
memset(rep->old_value1,0,SIZE);
memset(rep->old_value2,0,SIZE);
if(strcmp(buffer,"AT+REG1")==0) {
rep->operation=read_reg;
rep->flag=1;
}else if(strcmp(buffer,"AT+REG2")==0){
rep->operation=read_reg;
rep->flag=2;
}else if(strcmp(buffer,"AT+REG2")!=0 || strcmp(buffer,"AT+REG1")!=0){
token=strtok(buffer,"=");
while(token!=NULL){
take[i]=token;
token=strtok(NULL," ");
i++;
}
if(strcmp(take[0],"AT+REG1")==0 && strcmp(take[1],"?")==0){
rep->operation=info;
rep->flag=1;
}else if(strcmp(take[0],"AT+REG2")==0 && strcmp(take[1],"?")==0){
rep->operation=info;
rep->flag=2;
}else if(strcmp(take[0],"AT+REG1")==0 && take[1]!=NULL){
rep->operation=insert;
rep->flag=1;
//Scanning for errors
if(atoi(take[1])>16535 || atoi(take[1])<0)
return rep=NULL;
char rev;
if(!isEmpty(stack1)){
//take the old value from the stack and save it
rep->old_value1[c1.counter1]=pop(stack1);
c1.counter1++;
int num=atoi(take[1]);
rev= num;
push(rev,stack1);
}else{
//push the new value into the stack
int num=atoi(take[1]);
rev= num;
push(rev,stack1);
}
}else if(strcmp(take[0],"AT+REG2")==0 && take[1]!=NULL){
rep->operation=insert;
rep->flag=2;
//Scanning for errors
if(atoi(take[1])>3 || atoi(take[1])<1)
return rep=NULL;
char rev;
if(!isEmpty(stack2)){
rep->old_value2[c2.counter2]=pop(stack2);
c2.counter2++;
int num=atoi(take[1]);
rev=num;
push(rev,stack2);
}else{
int num=atoi(take[1]);
rev=num;
push(rev,stack2);
}
}else{
free(rep);
return(NULL);
}
}else{
free(rep);
return(NULL);
}
return rep;
}
void process_request(int fd){
fd_set readfd;
int status;
char *str;
char buffer[SIZE];
int read_num=0;
char *str1;
struct flock fl;
struct timeval timeout;
Request *request;
fl.l_type = F_RDLCK; /* read lock */
fl.l_whence = SEEK_SET; /* beginning of file */
fl.l_start = 0; /* offset from l_whence */
fl.l_len = 0; /* length, 0 = to EOF */
fl.l_pid = getpid(); /* PID */
//Clean buffer
memset(buffer,0,SIZE);
FD_ZERO(&readfd);
FD_SET(fd,&readfd);
timeout.tv_sec=100;
timeout.tv_usec=0;
status=select(40,&readfd,NULL,NULL,&timeout);
if(status==0){ //no data is receiving !
printf("Cannot receive data from client\n");
printf("\tTime Out\n");
exit(1);
}
//read from file descriptor
read_num=read(fd,buffer,sizeof(buffer));
if(read_num<0)perror("Error in reading\n");
if(read_num){
fcntl(fd, F_SETLKW, &fl); // set lock
str1=strdup(buffer);
request = parse_request(str1);
if(request){
switch(request->operation){
case info:
if(request->flag==1){
write(fd,"0-16535\n",20);
}else if(request->flag==2){
write(fd,"1|2|3\n",40);
}
break;
case read_reg:
if(request->flag==1){
//HERE IS THE PROBLEM!!!
t1=pop(stack1);
printf("%s\n",t1); // it understand this as int why ?
write(fd,&t1,5);
//---------------
}else if(request->flag==2){
t2=pop(stack2);
write(fd,&t2,sizeof(t2));
}
break;
case insert:
if(request==NULL)
write(fd,"INVINPUT\n",20);
write(fd,"OK\n",5);
break;
default:
printf("Something went wrong\n");
break;
}
if(request)
free(request);
}
}
fl.l_type = F_UNLCK;
fcntl(fd, F_SETLK, &fl); // unset lock
}
int isEmpty(char *stack){
if(stack==stack1){
if(top1==-1)
return 1;
return 0;
}else if(stack==stack2){
if(top2==-1)
return 1;
return 0;
}
}
int isFull(char *stack){
if(stack==stack1){
if(top1==STACK_SIZE)
return 1;
return 0;
}else if(stack==stack2){
if(top2==STACK_SIZE)
return 1;
return 0;
}
}
void push(char num,char *stack){
if(stack==stack1){
if(!isFull(stack1)){
printf("Eisagogh\n");
top1++;
//*(stack+top1)=num;
stack1[top1]=num;
}else{
printf("Error , push at stack1\n");
}
}else if(stack==stack2){
if(!isFull(stack2)){
top2++;
*(stack2+top2)=num;
}else
printf("Error , push at stack2\n");
}
}
char pop(char *stack){
char str_num;
if(stack==stack1){
if(!isEmpty(stack)){
printf("Eksagogh\n");
str_num=*(stack+top1);
top1--;
return str_num;
}else
printf("Error in pop item from stack1\n");
}else if(stack==stack2){
printf("me vlepeis edo ?\n");
if(!isEmpty(stack)){
str_num=*(stack+top2);
top2--;
return str_num;
}else
printf("Error in pop item from stack2\n");
}
}
Running :
CLIENT
AT+REG1=5
writing AT+REG1=5 command
Response:OK
AT+REG1
writing AT+REG1 command
Responce :
SERVER
[+] port opened succesfully!
push //it is the default value that I insert into the stack
[+] Connection starting !
pop // pops out the default value
push // seems that inserting the value 5 that client asked
pop // and now that pop is for writing to serial port in order client reads it (HERE IS THE PROBLEM) this is the point where I mention in the code that I have problem terminal seeing it as integer and not as char , go check this at process_requst function in server above.
If client sends although AT+REG1 he response the default value where server pops out from stack and send it in the point where the problem is . Please if anyone can help i would appreciate.