How to support both IPv4 and IPv6 connections

c++ winsock ipv6 sockets ipv4
Charles picture Charles · Oct 24, 2009 · Viewed 40.7k times · Source

I'm currently working on a UDP socket application and I need to build in support so that IPV4 and IPV6 connections can send packets to a server.

I was hoping that someone could help me out and point me in the right direction; the majority of the documentation that I found was not complete. It'd also be helpful if you could point out any differences between Winsock and BSD sockets.

Thanks in advance!

Answer

Martin v. Löwis picture Martin v. Löwis · Oct 24, 2009

The best approach is to create an IPv6 server socket that can also accept IPv4 connections. To do so, create a regular IPv6 socket, turn off the socket option IPV6_V6ONLY, bind it to the "any" address, and start receiving. IPv4 addresses will be presented as IPv6 addresses, in the IPv4-mapped format.

The major difference across systems is whether IPV6_V6ONLY is a) available, and b) turned on or off by default. It is turned off by default on Linux (i.e. allowing dual-stack sockets without setsockopt), and is turned on on most other systems.

In addition, the IPv6 stack on Windows XP doesn't support that option. In these cases, you will need to create two separate server sockets, and place them into select or into multiple threads.

Related questions

Converting C++ TCP/IP applications from IPv4 to IPv6. Difficult? Worth the trouble?

Over the years I've developed a small mass of C++ server/client applications for Windows using WinSock (Routers, Web/Mail/FTP Servers, etc... etc...). I’m starting to think more and more of creating an IPv6 version of these applications (…

Read More
MinGW linker error: winsock

I am using MinGW compiler on Windows to compile my C++ application with sockets. My command for linking looks like: g++.exe -Wall -Wno-long-long -pedantic -lwsock32 -o dist/Windows/piskvorky { there are a lot of object files } and I have …

Read More
Do I have to bind a UDP socket in my client program to receive data? (I always get WSAEINVAL)

I am creating a UDP socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP) via Winsock and trying to recvfrom on this socket, but it always returns -1 and I get WSAEINVAL (10022). Why? When I bind() the port, that does not happen, …

Read More