Unnecessarily difficult task of resolving hostname to ip

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Hi,

I'm having a nightmare doing something so, so simple in C++. All I want to do is input a hostname, and get its IP address. It is not something which should take hours and hours to work out.

Regardless whether I use the deprecated gethostbyname() or getaddrinfo(), nothing works. gethostbyname() returns 0.0.0.0, which is obviously wrong, and getaddrinfo() doesn't return anything at all. I don't want to use deprecated code, but neither works anyway.

What I have tried:

I've tried so, so many different variations of the same code, in excess of 20 by now. The most recent is

C++

struct addrinfo hints {}, *res{}, *res0{};
		
		memset(&hints, 0, sizeof(hints));
		hints.ai_family = AF_UNSPEC;
		hints.ai_socktype = SOCK_STREAM;
		getaddrinfo("www.google.com", "http", &hints, &res0);
		ip_address = res->ai_addr->sa_data;
		freeaddrinfo(res0);

Posted 1-Jul-18 11:50am

User 13204940

Updated 1-Jul-18 13:46pm

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Jochen Arndt · Answer 1 · 2018-07-01T13:46:00

Solution 1

I would expect an access violation because you are passing res0 but accesses res.

If a function is not working as expected, the first thing to do is to check the return value (which should be done anyway) and re-read the documentation (getaddrinfo function | Microsoft Docs[^], getaddrinfo(3) - Linux manual page[^]) which usually contains example code.

Posted 1-Jul-18 13:46pm

Jochen Arndt

Comments

[no name] 2-Jul-18 4:29am

Chances are, if you link me to code, I've already seen it. In this case, I've already tried that code, and I can't remember the result but it was either 0.0.0.0 or nothing.

Jochen Arndt 2-Jul-18 4:51am

I told you also that you are accessing a NULL pointer (at least in the posted code). What I have seen is that you have seen the example code and modified it in a way that it does not work.

Please note that all I can see is what you have posted. But you can try more like checking the return value. If the result is 0.0.0.0, that should be non zero.