KaiserJohaan KaiserJohaan - 2 months ago 23
C Question

retrieving ip and port from a sockaddr_storage

I've got a

sockaddr_storage
containing the ipv4 address and port of a remote host. I haven't seen these
struct
s before though and I'm not sure how to cast it into a
struct
where I can directly retrieve IP address and port number. I've tried googling the
struct
but haven't found anything. Any suggestions on how to do this?

Thanks

R.. R..
Answer

You can cast the pointer to struct sockaddr_in * or struct sockaddr_in6 * and access the members directly, but that's going to open a can of worms about aliasing violations and miscompilation issues.

A better approach would be to pass the pointer to getnameinfo with the NI_NUMERICHOST and NI_NUMERICSERV flags to get a string representation of the address and port. This has the advantage that it supports both IPv4 and IPv6 with no additional code, and in theory supports all future address types too. You might have to cast the pointer to void * (or struct sockaddr * explicitly, if you're using C++) to pass it to getnameinfo, but this should not cause problems.

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