winsock problems

HI,
I have been trying to get sockets to work but for some reason it does not work:

Code:

const char *ip_address = "127.0.0.1";

client=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(client==INVALID_SOCKET) {
return -1;
}


hostent *server_ip_address = gethostbyaddr(ip_address,sizeof(ip_address),AF_INET);

gethostbyaddr returns null for some reason although I have a server program running and listening and I am sure the server program works because I tested it with telnet. I am trying to use part of the example on this website:
http://www.codeproject.com/internet/winsockintro02.asp

Hopefully somebody can help me out. Thanks
Amish

Can you give us a WSAGetLastError().

Probably because you are passing sizeof(ip_address) which will return the size of const char* (4 on my system)

Declare ip_address as an array instead:

Code:

const char ip_address[] = "127.0.0.1";

Originally Posted by axr0284

HI,
I have been trying to get sockets to work but for some reason it does not work:

Code:

const char *ip_address = "127.0.0.1";

client=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(client==INVALID_SOCKET) {
return -1;
}


hostent *server_ip_address = gethostbyaddr(ip_address,sizeof(ip_address),AF_INET);

gethostbyaddr returns null for some reason although I have a server program running and listening and I am sure the server program works because I tested it with telnet. I am trying to use part of the example on this website:
http://www.codeproject.com/internet/winsockintro02.asp

Hopefully somebody can help me out. Thanks
Amish

As, JaWiB pointed out, you need to pass the length of the ip adrress instead of the size of a pointer. However, I would recommend using strnlen (if using C), instead of declaring an array because your code would document itself this way.

Thanks for the reply. I tried everything that you said and checked that the length passed to the function was correct this time but it still returns NULL. Error returned by WSAGetLastError() is as follows and description from msdn:
WSANO_DATA
11004

Valid name, no data record of requested type.
The requested name is valid and was found in the database, but it does not have the correct associated data being resolved for. The usual example for this is a host name-to-address translation attempt (using gethostbyname or WSAAsyncGetHostByName) which uses the DNS (Domain Name Server). An MX record is returned but no A record—indicating the host itself exists, but is not directly reachable.

I am posting the whole code. Maybe the error is elsewhere. I'll read the website where I got this again just in case:

Code:

SOCKET client;
WSADATA wsaData;
sockaddr_in server;
int wsaret=WSAStartup(0x101,&wsaData);
if(wsaret!=0)
    {
        return 0;
    }


string ip_address = "127.0.0.1";

const char *ip_address_char= ip_address.c_str();

client=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(client==INVALID_SOCKET) {
return -1;
}


int length = strlen(ip_address.c_str());
hostent *server_ip_address = gethostbyaddr(ip_address.c_str(),strlen(ip_address.c_str()),AF_INET);
int err = WSAGetLastError();
server.sin_addr.S_un.S_addr /*=*((unsigned long*)server_ip_address->h_addr);*/= (u_long) server_ip_address->h_addr_list[0];
server.sin_family = AF_INET;
server.sin_port = htons((u_short)20248);


if(connect(client,(struct sockaddr*)&server,sizeof(server)))
{
closesocket(client);
return -1;	
}

const char *output_message = "test";
	
char input_message[512];
	
send(client,output_message,sizeof(output_message),0);

int y = 0;

while(y=recv(client,input_message,512,0))
{
//f.Write(buff,y);
cout << input_message << "/n";
}

closesocket(client);
WSACleanup();

    return 0;

Thanks for the help everybody. I really appreciate it.
Amish

Ok Figured it out.
I would seem like gethostbyaddr() expects the first parameter to be a binary representation of the Internet address. Therefore the following conversion needs to be used before calling that function:

Code:

string ip_address = "127.0.0.1";
unsigned int addr;
addr= inet_addr(ip_address.c_str());
hostent *server_ip_address = gethostbyaddr((char *) &addr, 4, AF_INET);

It's a little strange to me why gethostbyaddr() would not just take a regular char representation of the ip address. Anyways now server_ip_address structure gets filled correctly. Thanks everybody for helping out.
Amish