c programming: stopping endless loops [closed] - c

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I have been trying to get my head around validating the code, a.k.a stopping the program from breaking and entering the endless loops but I find it quite difficult.
So far I have come across multiple points in the program where the user can break it by entering the wrong input for example with the main menu if the user enters a letter or symbol instead of a number the program enters the endless loop, so a basic guide on validating would be helpful.
#include <stdio.h>
#include <stdlib.h>
struct packet{
int source;
int destination;
int type;
int port;
char data[50];
};
void main ()
{
struct packet s[50]; //Array for structure input
int choice;
int customerCount = 0, ii = 0;
while (customerCount <= 50){
printf("What would you like to do?\n");
printf("\t1) Add a packet.\n");
printf("\t2) s all packets.\n");
printf("\t3) Save packets.\n");
printf("\t4) Clear all packets.\n");
printf("\t5) Quit the programme.\n");
scanf("%i", &choice);
switch (choice)
{
case 1: printf("\n****Adding a packet*****\n");
printf("Where is the packet from?\n");
scanf("%i", &s[customerCount].source);
printf("Where is the packet going?\n");
scanf("%i", &s[customerCount].destination);
printf("What type is the packet?\n");
scanf("%i", &s[customerCount].type);
printf("What is the packet's port?\n");
scanf("%i", &s[customerCount].port);
printf("Enter up to 50 characters of data.\n");
scanf("%s", s[customerCount].data);
customerCount++;
break;
case 2: printf("\nDisplaying Infomation\n");
for(ii = 0; ii < customerCount; ii++) {
printf("\nSource: %d", s[ii].source);
printf("\nDestination: %d", s[ii].destination );
printf("\nType : %d", s[ii].type);
printf("\nPort : %d", s[ii].port);
printf("\nData: %s\n---\n", s[ii].data);
}
break;
case 3: break;
case 4: break;
case 5: break;
default: printf("\nThis is not a valid choice, please choose again\n\n");
break;
}
}
}

Answer 1

scanf returns the number of arguments it successfully scanned.
Checking for proper input and rejecting bad input can be as simple as:
printf("Where is the packet from?\n");
while(scanf("%i", &s[customerCount].source) != 1)
{
while(getchar() != '\n')
continue;
}
This is not very robust, however, and something like validating user input should be very robust. Assume the user will always enter wrong input... it's sad but true.