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Re: [lwip-users] DNS host not resolving using lwip_gethostbyname functio

From: Sergio R. Caprile
Subject: Re: [lwip-users] DNS host not resolving using lwip_gethostbyname function using ppp over serial
Date: Mon, 02 Mar 2015 10:31:11 -0300
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

I will give you the best advise I can give you. Two of them, and for
free. Well actually three:

1 - Don't expect some random one to help you, if you don't provide a
clue on what you are doing. Do you know what you are doing ?
2 and 3 - At bottom

Here's what I can extract from your writing
You seem to be working with some hardware connected to some GPRS modem.
You are running PPP over GPRS to connect to whoknowswhere, where there
is some who seems to be a DNS server.
You seem to be using the netconn API, which I don't know and so I'm not
able to help you, but if you provide that info on your msgs, maybe one
who knows it gets attracted by the subject line.
You seem to do some calls to the API, expecting to get some results.
Maybe if you actually explain what you are doing, maybe someone will
actually tell you what you are doing wrong.
You seem to have seen the (supposedly) DNS server response is not coming
back. Did you actually see the question going out ? Have you checked it
is OK and consistent ?
But even before getting there, have you ever checked your routing and
your port works OK ? Have you ever tried a known to work example ? Have
you pinged google or yahoo ?

2 - First: check your port works, try known to work examples, try simple
stuff, make sure it works. E.g.: PPP over a modem to a known to work ISP
phone number. Yes, use other hardware if you have to, or use Ethernet,
you MUST be sure your port works. Second: check your connection to the
world works, repeat the former tests over your connection. You MUST be
sure your connection works. Third: read the wiki. Know how to use your
system and your functions. Fourth: if you have a problem, read the wiki
again and learn how to properly report an issue or ask for help.

Subject: lwip_gethostbyname (netconn) returns ERR_VAL
Hello, I'm using netconn on a blablabla port of lwIP 1.4.1 (release),
the port has been tested and it works OK. Connection is OK, I can ping
the DNS and it is known to work (I'm using it from other machines). When
I call lwip_gethostbyname() I get ERR_VAL (-6), the DNS client has been
properly initialized, here is my code:
function()    /* I don't know netconn, so I can't write a proper code
example */
    call to init dns()
    call to lwip_gethostbyname (parameters)
    here I can see the error
    nothing else
Attached you can find the capture I did with wireshark. I'm not
proficient to understand the DNS dialog, so please help me on this one too.

Best regards

3 - Never follow old ugly women and advise (old engllish (american ?)


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