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Re: [lwip-users] lwip minimal example, echo server

From: Matthias Dübon
Subject: Re: [lwip-users] lwip minimal example, echo server
Date: Tue, 7 Oct 2014 15:37:39 +0200

Hello again,

forget my last mail, I think I found something like a real reason for
the not working minimal example. After some debugging (starting with
the not working ARP resolution) I found that the netif flags are not
initialised in the mintapif_init in mintapif.c. After adding:


everything is working fine.


On Tue, Oct 7, 2014 at 12:39 PM, Matthias Dübon
<address@hidden> wrote:
> Hello Sergio,
> thanks for your support, I found my mistake, I changed the IP address
> from to because the is already
> taken in my network. When using everything is working
> fine. Hence I think I have to read something more about tap devices
> and default gateways.
> best
> Matthias
> On Fri, Oct 3, 2014 at 3:27 PM, Sergio R. Caprile <address@hidden> wrote:
>> OK, here I go...
>> The UN*X examples use a tun/tap device, and there is a specific
>> configuration parameter for different flavors of it. Check the Makefile
>> for this, did you ?
>> #To compile for linux: make ARCH=linux
>> #To compile for cygwin: make ARCH=cygwin
>> #To compile for openbsd: make ARCH=openbsd
>> ARCH=linux
>> Once you have the correct tun or tap device, it will show up in your
>> ifconfig and you will be able to ping the lwIP stack as a new machine on
>> a new network, which is what you should do first when debugging
>> networking problems.
>> In main.c:
>>   /* startup defaults (may be overridden by one or more opts) */
>>   IP4_ADDR(&gw, 192,168,0,1);
>>   IP4_ADDR(&ipaddr, 192,168,0,2);
>>   IP4_ADDR(&netmask, 255,255,255,0);
>> So, will be the address of the gateway in your machine to
>> "the lwIP network", via a tun or tap interface. In Linux seems to be tap
>> tap0      Link encap:Ethernet  HWaddr 86:99:D8:CE:27:DC
>>           inet addr:  Bcast:  Mask:
>>           inet6 addr: fe80::8499:d8ff:fece:27dc/64 Scope:Link
>>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>>           TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
>>           collisions:0 txqueuelen:500
>>           RX bytes:0 (0.0 b)  TX bytes:468 (468.0 b)
>> The specifics to get the tap working are beyond my knowledge, I remember
>> I just followed a tutorial. The interface will be up once the example is
>> running, and will dissappear after that.
>> Anyway, you should be able to ping that interface to check if the tap is
>> working.
>> And,  will be your "lwIP machine" address, you should be
>> able to ping it
>> address@hidden minimal]# ping
>> PING ( 56(84) bytes of data.
>> 64 bytes from icmp_seq=1 ttl=255 time=8.76 ms
>> 64 bytes from icmp_seq=2 ttl=255 time=9.66 ms
>> --- ping statistics ---
>> 2 packets transmitted, 2 received, 0% packet loss, time 999ms
>> rtt min/avg/max/mdev = 8.766/9.214/9.663/0.458 ms
>> and you should be able to telnet to it in port 7, cause no one knows if
>> your
>> SimpleEchoClient really works, although you probably will.
>> address@hidden minimal]# telnet 7
>> Trying
>> Connected to
>> Escape character is '^]'.
>> hola
>> hola
>> You probably noticed I run this as root... there are some permissions
>> associated to the tap interface, and I'm lazy enough to change them.
>> Anyway, you should see something like this:
>> tapif: tapif_init: open: Permission denied
>> if that is the case.
>> _______________________________________________
>> lwip-users mailing list
>> address@hidden
>> https://lists.nongnu.org/mailman/listinfo/lwip-users

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