Multicast speed limits issue!!

[chiyuwang]

I recently made a very small test program, almost same as the example from msdn

https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx

I change the source code a little bit, so that it will be multicast, and it keepsending data as soon as possible, and I will look at task manager to see how much network is utilized.

If ip address is a multicast address, the program only uses 10% of the network bandwidth.
While the program use almost 100% bandwidth, if the ip address is a unicast address.

2 PC connected to a switch, both use a fixed ip address, (There is no rounter involved)

I like to make multicast tranportation faster, so that my application can have better performance. I wonder if there is any setting in windows or somewhere else for making multicast fast, or there is any function for the multicast socket.

Please please help.

#ifndef UNICODE
#define UNICODE
#endif

#define WIN32_LEAN_AND_MEAN

#include <winsock2.h>
#include <Ws2tcpip.h>
#include <stdio.h>

// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")

int main()
{

	int iResult;
	WSADATA wsaData;

	SOCKET SendSocket = INVALID_SOCKET;
	sockaddr_in RecvAddr;

	unsigned short Port = 27015;

	char SendBuf[1024];
	int BufLen = 1024;

	//----------------------
	// Initialize Winsock
	iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
	if (iResult != NO_ERROR) {
		wprintf(L"WSAStartup failed with error: %d\n", iResult);
		return 1;
	}

	//---------------------------------------------
	// Create a socket for sending data
	SendSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (SendSocket == INVALID_SOCKET) {
		wprintf(L"socket failed with error: %ld\n", WSAGetLastError());
		WSACleanup();
		return 1;
	}
	//---------------------------------------------
	// Set up the RecvAddr structure with the IP address of
	// the receiver (in this example case "192.168.1.1")
	// and the specified port number.
	RecvAddr.sin_family = AF_INET;
	RecvAddr.sin_port = htons(Port);
	RecvAddr.sin_addr.s_addr = inet_addr("234.10.10.10");

	//---------------------------------------------
	// Send a datagram to the receiver
	char ttl = 0;
	int r = setsockopt(SendSocket, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
	wprintf(L"Sending a datagram to the receiver...\n");
	while (true) {
		iResult = sendto(SendSocket,
			SendBuf, BufLen, 0, (SOCKADDR *)& RecvAddr, sizeof(RecvAddr));
		if (iResult == SOCKET_ERROR) {
			wprintf(L"sendto failed with error: %d\n", WSAGetLastError());
			closesocket(SendSocket);
			WSACleanup();
			return 1;
		}
	}
	//---------------------------------------------
	// When the application is finished sending, close the socket.
	wprintf(L"Finished sending. Closing socket.\n");
	iResult = closesocket(SendSocket);	
	if (iResult == SOCKET_ERROR) {
		wprintf(L"closesocket failed with error: %d\n", WSAGetLastError());
		WSACleanup();
		return 1;
	}
	//---------------------------------------------
	// Clean up and quit.
	wprintf(L"Exiting.\n");
	WSACleanup();
	return 0;
}