Hello,
I am connecting QNX and Windows under one network.
I am using nic for wifi on QNX.
I can ping from both side and works perfectly.

Testing of Server/Client app (Ubuntu and Windows)

Data transfer rate : 1.0 MBps (Approx)
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Testing of Server/Client app (Ubuntu and Windows)

Data transfer rate : 150 KBps (Approx)

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I am using same code for both QNX and Ubuntu as Server and Windows as Client.

Question 1: Why is vast difference between data transfer rate between these process? 
Question 2: What is possible reason behind this problem?
Question 3: How to solve this problem?

I am also attaching codes file!

Requirment,

Execute server side,
./ (executable file name) 2222

-'2222' is port no.

Execute Client side 
(filename .exe) (IP address of QNX)