Need help in client input restriction..

I received an assignment which ask for simple calculations between server and client such as addition, subtraction, multiplication, division, etc.

Currently, I had finished the calculation part, where client could input in 2 numbers and the operation they want to the server so the server could do the calculation and send back the result to client. The problem I'm facing now is, how could I restrict the client side so that they are only allowed to input numbers and not characters?

This is a small part of my codes :

Code:

// Reply first number
	char firstnum[256];
	cin >> firstnum;

	send(	theSocket,				// Connected socket
		firstnum,				// Data buffer
		strlen(firstnum),			// Length of data
		0);

Anyhelp would be appreciated, thanks.

use isdigit() to check firstnum[0] thru firstnum[strlen(firstnum)-1] in a for loop. Tip: watch out for '\n' characters at end of input.

another way is to read the input using fgets() to read stdin, then parse firstnum using sscanf()

the second method works very well if you do it right.

hmm, didn't quite get what you mean at there, since I'm pretty new to C++... >_>

Anyway, just an idea :

Would it work, if I put the 24 alphabets into an array and scan the input with it so it could detect characters and alert the client?

Originally Posted by cyrus2k

hmm, didn't quite get what you mean at there, since I'm pretty new to C++... >_>

Anyway, just an idea :

Would it work, if I put the 24 alphabets into an array and scan the input with it so it could detect characters and alert the client?

Excuse me if I was vague. Too many late nights has that effect on me.

Forget the stuff I told you... those are old C language ways of validating input. You can do it very easily in C++ like this...

Code:

int n=0;

cout << "Enter first number: ";
cin >> n;
if (cin.fail())
    cout << "Input error, please try again" << endl;
else
    cout << "You entered the number " << n << endl;

If the user enters a non-decimal character before any decimal characters, the call to "if (cin.fail())" will evaluate true.

So, for example, the input "123ttt" will put the number 123 into n, while the input "ttt321" will raise an error.

pretty simple, huh?

-Rog