Resolve winsock deprecation

[Brett208]

Looks similar to deprecated functions in NetHelper/miniupnp we fixed earlier.

Warning C4996 'gethostbyname': Use getaddrinfo() or GetAddrInfoW() instead or define _WINSOCK_DEPRECATED_NO_WARNINGS to disable deprecated API warnings NetFixClient \netfixclient\opunettransportlayer.cpp 916

Warning C4996 'inet_addr': Use inet_pton() or InetPton() instead or define _WINSOCK_DEPRECATED_NO_WARNINGS to disable deprecated API warnings NetFixClient \netfixclient\opunettransportlayer.cpp 910

[DanRStevens]

For reference:

http://man7.org/linux/man-pages/man3/gethostbyname.3.html
http://man7.org/linux/man-pages/man3/getaddrinfo.3.html

OutpostUniverse/NetHelper@acb916a

http://man7.org/linux/man-pages/man3/inet_addr.3p.html
http://man7.org/linux/man-pages/man3/inet_pton.3.html

Edit:
For a general overview of socket programming, this might also be a good reference:
http://beej.us/guide/bgnet/html/multi/syscalls.html

[DanRStevens]

I was looking at this code. Both deprecated calls are in OPUNetTransportLayer::GetHostAddress. The method is used to convert a string form address to an address structure. It supports either numeric dotted IPv4 addresses (Ex: "192.168.1.2:47800"), or DNS names (Ex: "netfix.outpost2.net:47800") which causes a DNS lookup.

Both of these uses are supported by the new getaddrinfo method. Hence, both deprecated methods can be replaced by a single new method. Quite likely the function can be shortened.

I propose the following as a candidate replacement function:

sockaddr OPUNetTransportLayer::StringToAddress(const char* addressString) {
	// Skip any leading spaces
	while (addressString[0] == ' ' || addressString[0] == '\t')
		addressString++;

	// Break string into hostname and port components
	const char* portNumString = strchr(addressString, ':');
	// Advance past ":"
	portNumString += portNumString != nullptr ? 1 : 0;

	// Convert address to struct form
	addrinfo hints = {0, AF_INET, SOCK_DGRAM, IPPROTO_UDP };
	addrinfo* addressLinkedList;
	auto errorCode = getaddrinfo(addressString, portNumString, &hints, &addressLinkedList);
	if (errorCode) {
		throw std::runtime_error(gai_strerror(errorCode));
	}
	if (addressLinkedList->ai_addr == nullptr) {
		throw std::runtime_error("No candidate addresses");
	}
	// Simplification: Just return the first address in the list
	auto address = *addressLinkedList->ai_addr;
	freeaddrinfo(addressLinkedList);

	return address;
}

There are a couple of caveats though. One is the simplification used by this function, where it just returns the first found address. Another is that it copies the full struct to the output, whereas the old method passed in a struct, which then had specific fields initialized. Fields that were not set by the old method could be pre-initialized so they'd have known output values. This was used in one place to form a broadcast address used to search for games.

Additionally, the type of address was changed to the more generic sockaddr, rather than the IPv4 specific sockaddr_in. I believe we should use the more generic struct name whenever possible, though the specific name is used in quite a few places, so updates may be somewhat widespread.

I'd like to see if there are a few step-wise refactorings I can do, so this isn't just one big huge mess when it lands.

---

Edit: It seems sockaddr is the common fields at the beginning of both sockaddr_in (IPv4) and sockaddr_in6 (IPv6). That means the copy/return above won't quite work right, as it may slice what should be a larger struct.