Hi everyone,

I'm trying to get my client to send a packet with some text and my server to receive the packet and display the text.

Currently I'm trying this locally so what I'm doing now is the following.

1) I send some text using sendto()

2) I try to receive the data using recvfrom()

The problem is that the recvfrom data doesn't seem to receive a packet. The two methods that I'm using are coded like this:

Used in step 1:

bool Networking::SendPacket(const void * message)
{
	// Set up address to send the packet to
	unsigned int a = 127;
    unsigned int b = 0;
    unsigned int c = 0;
    unsigned int d = 1;
    unsigned short port = 2890;

	unsigned int destination_address = ( a << 24 ) | ( b << 16 ) | ( c << 8 ) | d;
    unsigned short destination_port = port;

    address.sin_family = AF_INET;
    address.sin_addr.s_addr = htonl( destination_address );
    address.sin_port = htons(destination_port);

	// Try to send the packet
	int sent_bytes = sendto(handle, (const char*)message, sizeof(message), 0, (sockaddr*)&address, sizeof(sockaddr_in));

	// Check if the packet was sent successfully
    if (sent_bytes != sizeof(message))
    {
        printf("failed to send packet: return value = %d\n", sent_bytes);
        return false;
    }
	else
	{
		cout << "this packet was successfully sent: " << (const char*)message << "\n";
		return true;
	}

	return true;
}

Used in step 2:

void Networking::ReceivePacket()
{	
	unsigned char packet_data[256];

	#if PLATFORM == PLATFORM_WINDOWS
		typedef int socklen_t;
	#endif
			
	sockaddr_in from;
	socklen_t fromLength = sizeof( from );

	int received_bytes = recvfrom(handle, (char*)packet_data, sizeof(packet_data), 0, (sockaddr*)&from, &fromLength );

	if (received_bytes <= 0)
		return;

	cout << "RECEIVED DATA: " << (char*)packet_data << "\n";
}

Does anyone see what I'm doing wrong?

Thanks in advance

replace all your 'destination_address' code with something more like:

// get pointer to address
unsigned char *addr = (unsigned char *)&address.sin_addr.s_addr;

// set address directly
addr[0] = 127;
addr[1] = 0;
addr[2] = 0;
addr[3] = 1;

try using 'sizeof(sockaddr_in)' for 'fromLength' instead of 'sizeof(from)'... try using a #define value for the size of 'packet_data', as well as using it to replace 'sizeof(packet_data)'..

make sure that whatever is receiving the packet has called 'recvfrom' before whatever is sending the packet calls 'sendto', otherwise, you will send the packet, it will disappear in the void of datagram, and the receiver will be called after the packet disappears. that is the nature of UDP/datagram, data disappears if nobody is listening for it before it is sent (along with network noise and collisions causing packets to be disregarded and lost).

good luck.

Hi guys. Thanks for the quick replies.

@RadioTeeth: Why should I do the destination_address differently?

@hplus0603: Yes, handle is a valid socket and it's bound to the right ports and everything.

sendto() returns 4

recvfrom() returns -1 in the current state but I'll be changing things now so I'll keep you updated what they return if you want.

EDIT: So I changed some things like Radioteeth suggested but that doesn't seem to change anything. I have this code to test out if my program receives it's own messages:

pNetworkObject->ReceivePacket();
pNetworkObject->SendPacket("hello");

pNetworkObject->SendPacket("second hello");
pNetworkObject->ReceivePacket();

I'll check how I should send the data properly.

I'm currently sending this (const char*)message. Where message starts as a void*.

When I cout this data it outputs the text so I don't think that's the problem?

And I'm running a 64-bit windows 7. But this is just my Visual Studio setup that's 32-bit or not?

errno outputs "No Error".

I use printf(strerror(errno)) to show to error on my screen.

handle is the same if both cases yes. I don't think this could be a problem?