# Socket PDU

**URL:** <https://www.ruby-forum.com/t/socket-pdu/241205>\
**Category:** GNU Radio\
**Created:** [May 18, 2014, 9:47pm UTC](https://www.ruby-forum.com/t/socket-pdu/241205 "2014-05-18T21:47:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [May 18, 2014, 9:47pm UTC](https://www.ruby-forum.com/t/socket-pdu/241205/1 "2014-05-18T21:47:00Z")

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Hello ,  
I have 2 questions, please:  
1- If I put a vector source as input or file source & I choose " No  
repeat"  
for the input , I find that no output is written in file sink ! why ?  
2- I want to receive real time voice packets from an application running  
on  
another lap which is connected to the second lap (which has GNU Radio.)  
using Ethernet Cable.  
First : I found a block " socket PDU" in GNU Radio , if I used it , Do I  
need to write the code of socket (client & server) ?  
Second : I write IP of 1st lap & the port number used by the application  
in  
the UDP Third : I connected 3 blocks : " UDP source " then "socket PDU  
"  
then “PDU to stream tagged” , I don’t know why I have an error in the  
connection of UDP source & socket PDU ! Please tell me what is the  
problem  
?(as the arrow is red)  
Thanks 🙂

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**Author:** ![Sara\_ChSSrif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/7ba0ec/32.png) [@Sara\_ChSSrif](https://www.ruby-forum.com/u/Sara_ChSSrif)\
**Post date:** [May 18, 2014, 10:10pm UTC](https://www.ruby-forum.com/t/socket-pdu/241205/2 "2014-05-18T22:10:24Z")

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Hi sara,  
For your problem of the empty file sink. What did you use exactly, as  
blocks, between the file source and the file sink?

–  
View this message in context:  
[http://gnuradio.4.n7.nabble.com/Socket-PDU-tp48297p48298.html](http://gnuradio.4.n7.nabble.com/Socket-PDU-tp48297p48298.html)  
Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).

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**Author:** ![Sara\_ChSSrif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/7ba0ec/32.png) [@Sara\_ChSSrif](https://www.ruby-forum.com/u/Sara_ChSSrif)\
**Post date:** [May 19, 2014, 4:07pm UTC](https://www.ruby-forum.com/t/socket-pdu/241205/3 "2014-05-19T16:07:56Z")

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On Sun, May 18, 2014 at 3:45 PM, Sara Chérif [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Hello ,  
> I have 2 questions, please:  
> 1- If I put a vector source as input or file source & I choose " No  
> repeat" for the input , I find that no output is written in file sink ! why  
> ?

You could try this in unbuffered mode. I just tried it with the items in  
the vector source and it worked fine in both buffered and unbuffered,  
but  
unbuffered mode might help here.

> Thanks 🙂

Only like signals can connect to each other. You’ll notice different  
colors  
of the ports. That’s because the UDP source and Socket PDU use two  
completely different types of data connections. See “Help-\>Types” in GRC  
and notice that the Socket PDU uses async messages, which you cannot  
connect to a data stream like the UDP source.

Read this for an intro to the message passing system:

[http://gnuradio.org/doc/doxygen/page\_msg\_passing.html](http://gnuradio.org/doc/doxygen/page_msg_passing.html)

Tom