# Problem with "TCP Source" module in the client mode

**URL:** <https://www.ruby-forum.com/t/problem-with-tcp-source-module-in-the-client-mode/239530>\
**Category:** GNU Radio\
**Created:** [March 3, 2014, 5:59pm UTC](https://www.ruby-forum.com/t/problem-with-tcp-source-module-in-the-client-mode/239530 "2014-03-03T17:59:24Z")\
**Posts on this page:** 4\
**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:** [March 3, 2014, 5:59pm UTC](https://www.ruby-forum.com/t/problem-with-tcp-source-module-in-the-client-mode/239530/1 "2014-03-03T17:59:24Z")

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Hi all!

I am trying to build following simple scheme:

Signal source --\> TCP Sink (server mode) \<---- TCP Source (client mode)  
–\> GUI Scope Sink

It’s strange but this simple scheme isn’t working.

sockstat shows me:

USER COMMAND PID FD PROTO LOCAL ADDRESS FOREIGN  
ADDRESS  
igor python2.7 56206 11 tcp4 10.21.32.6:21950 10.21.32.6:12000

Looks like communication between tcp sink and tcp source blocks has been  
established, but tcpdump doesn’t show any packets

I decided to check first part of my scheme (Signal source + TCP Sink),  
and connected using netcat utility to the tcp sink port. All looks OK,  
the values come as expected.

Can anybody explain, why this simple scheme doesn’t work?

Best regards,  
Igor

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**Author:** ![Igor\_V](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/96bed5/32.png) [@Igor\_V](https://www.ruby-forum.com/u/Igor_V)\
**Post date:** [March 4, 2014, 9:32am UTC](https://www.ruby-forum.com/t/problem-with-tcp-source-module-in-the-client-mode/239530/2 "2014-03-04T09:32:58Z")

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On 03.03.2014 17:57, Igor V. wrote:

> Hi all!
> 
> I am trying to build following simple scheme:
> 
> Signal source → TCP Sink (server mode) \<---- TCP Source (client mode)  
> → GUI Scope Sink
> 
> It’s strange but this simple scheme isn’t working.

Are you running both sub-flowgraphs in the same GRC canvas? I just tried  
this in 2 canvases and it works. It _should_ work from one, but I’m not  
sure GRC is setting things up right.

In any case, try 2 canvases.

M

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**Author:** ![Igor\_V](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/96bed5/32.png) [@Igor\_V](https://www.ruby-forum.com/u/Igor_V)\
**Post date:** [March 21, 2014, 5:53pm UTC](https://www.ruby-forum.com/t/problem-with-tcp-source-module-in-the-client-mode/239530/3 "2014-03-21T17:53:56Z")

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**Author:** ![Igor\_V](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/96bed5/32.png) [@Igor\_V](https://www.ruby-forum.com/u/Igor_V)\
**Post date:** [March 23, 2014, 6:11pm UTC](https://www.ruby-forum.com/t/problem-with-tcp-source-module-in-the-client-mode/239530/4 "2014-03-23T18:11:38Z")

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On 03/21/2014 05:52 PM, Tommy T. II wrote:

> Dear Martin,
> 
> Sorry for the delayed response. My code is all written in C++; I am not  
> using the GRC. These canvasses; are they separate top blocks?

Yes, and different processes.

M