Stuck - Need a little help

Hi I've tried for a few hours to figure this out - but the solution is escaping me.

This is a snippet of code for a program I am writing in C. iServerListenPort has been previously assigned.

Here is the code that does not work. It crashes after entering the IP address

Code:

char *serverip;
printf("Please enter a IP address of the server you wish to connect to\n");
scanf("%s",&serverip);
printf("\nConnecting to %s Port %d\n", serverip, iServerListenPort);
if(ClientSocketObject.Connect(serverip , iServerListenPort))
{
    printf("Client Connected\n");
}

This code Does work

Code:

char *serverip = "192.168.2.179";
printf("\nConnecting to %s Port %d\n", serverip, iServerListenPort);
if(ClientSocketObject.Connect(serverip , iServerListenPort))
{
   printf("Client Connected\n");
}

Here is the definition for socketobject.connect

Code:

bool Connect(char* szServerAddress, int iPort)

Thank-You very much for any help!!

Probably because scanf() has a nasty habit of stopping it's scan of char's whenever it encounters something it doesn't expect.

Check what scanf is actually scanning into that variable, I'll bet it's not what you were expecting.

You may want to use something like fgets(yourstringbuffer, sizeof(yourstringbuffer) - 1, stdin).

Try
char serverip[100];
Not
char *serverip;

Ah - Scanf was messing with my variable-- Thank-You very much Adak and Esbo - solved my problem..

I'm going to be much more careful with scanf going forward.

The problem was you declared a variable pointer but it was not pointing at any 'free space'
it was pointing at address 0000 which is where scanf tries to store what you type in.
It is likely it is illegal to write there or that you will overwrite something important.

And the fact you're most likely reading the line-break (\n) into the address.

If you use fgets() ensure you lop the trailing \n off, see the FAQ.

Code:

scanf("%s",&serverip);

Perpahs you dont need to send the address of the string. It should have been just the string. shich as serverip.

Code:

char server[100];

fgets(server,strlen[server],stdin);

ssharish2005

Originally Posted by Adak

Probably because scanf() has a nasty habit of stopping it's scan of char's whenever it encounters something it doesn't expect.

Check what scanf is actually scanning into that variable, I'll bet it's not what you were expecting.

You may want to use something like fgets(yourstringbuffer, sizeof(yourstringbuffer) - 1, stdin).

Why -1? fgets() includes the NULL terminator... Your just wasting 1 entire byte :O!

fgets(server,strlen[server],stdin);

Uh-Oh!..

strlen is a function so strlen()

and NEVER call it on the not initialized string...

should be
fgets(server,sizeof server,stdin);

The problem was you declared a variable pointer but it was not pointing at any 'free space'
it was pointing at address 0000 which is where scanf tries to store what you type in.
It is likely it is illegal to write there or that you will overwrite something important.

No, it was an uninitialized pointer. There's a big difference between a NULL pointer and an uninitialized pointer. In this case, the pointer was pointing at some random location in memory. The result is the same, though. Segmentation fault.