# UDP sender/receiver what the heck am I doing wrong **URL:** \ **Category:** GNU Radio\ **Created:** [July 14, 2014, 5:22pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954 "2014-07-14T17:22:44Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [July 14, 2014, 5:22pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/1 "2014-07-14T17:22:44Z")
Attached, you’ll find a pair of very-simple .grcs One is a UDP sender (using a pair of UDP sinks) The other is a UDP receiver (using a pair of UDP sources) The sender clearly works, as verified by ‘tcpdump’ at the receiving system. The ports are correct, etc. But _nothing_ is coming out of the UDP sources. My MTU is 1500, so the UDP frame size of 1472 is correct. And, I’ll repeat, ‘tcpdump’ sees the traffic. ---
**Author:** ![Marcus\_DSLeech](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Marcus\_DSLeech](https://www.ruby-forum.com/u/Marcus_DSLeech)\ **Post date:** [July 14, 2014, 5:48pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/2 "2014-07-14T17:48:23Z")
I saw something similar last week. ---
**Author:** ![Marcus\_DSLeech](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Marcus\_DSLeech](https://www.ruby-forum.com/u/Marcus_DSLeech)\ **Post date:** [July 14, 2014, 6:02pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/3 "2014-07-14T18:02:06Z")
On 07/14/2014 11:47 AM, John M. wrote: > I saw something similar last week. Opened up firewall rules. That didn’t help. But netcat could see the traffic, so it’s being delivered up to userland. ---
**Author:** ![Marcus\_DSLeech](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Marcus\_DSLeech](https://www.ruby-forum.com/u/Marcus_DSLeech)\ **Post date:** [July 14, 2014, 6:02pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/4 "2014-07-14T18:02:06Z")
Also saw the same thing. =) ---
**Author:** ![Marcus\_DSLeech](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Marcus\_DSLeech](https://www.ruby-forum.com/u/Marcus_DSLeech)\ **Post date:** [July 14, 2014, 6:14pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/5 "2014-07-14T18:14:39Z")
On 07/14/2014 12:00 PM, John M. wrote: > Also saw the same thing. =) You can’t leave the bind-addr blank–set it to the interface addy over which you expect packets to arrive, that works. I suspect that there’s some missing code to deal properly with a “promiscuous bind” in the UDP source block. – Marcus L. Principal Investigator Shirleys Bay Radio Astronomy Consortium > **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org)** > > Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami. ---
**Author:** ![Marcus\_DSLeech](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Marcus\_DSLeech](https://www.ruby-forum.com/u/Marcus_DSLeech)\ **Post date:** [July 14, 2014, 7:05pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/6 "2014-07-14T19:05:22Z")
On 07/14/2014 12:36 PM, Mike J. wrote: > Set the bind address to ‘0.0.0.0’ to listen on all interfaces. This > would be a good default setting. Yup, this works. That was one of my test-cases _before_ I changed the firewall rules… ---
**Author:** ![Marcus\_DSLeech](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Marcus\_DSLeech](https://www.ruby-forum.com/u/Marcus_DSLeech)\ **Post date:** [July 14, 2014, 6:38pm UTC](https://www.ruby-forum.com/t/udp-sender-receiver-what-the-heck-am-i-doing-wrong/230954/7 "2014-07-14T18:38:30Z")
Set the bind address to ‘0.0.0.0’ to listen on all interfaces. This would be a good default setting. – Mike J. M0MIK BSc MIET Email: removed\_email\_address@domain.invalid Web: [http://scanoo.com](http://scanoo.com)