I ran the test on a small-buffer size (0x7fff) and the test was successful.  On QNX website, its worded as follows: 

http://www.qnx.com/developers/docs/6.3.0SP3/neutrino/lib_ref/g/getsockopt.html?lang=de#SO_RCVBUF

"Gets or sets the normal buffer sizes allocated for output (SO_SNDBUF) and input (SO_RCVBUF) buffers. You can increase 
the buffer size for high-volume connections, or decrease it to limit the possible backlog of incoming data. The system 
places an absolute limit on these values and defaults them to at least 16K for TCP sockets"

I tried to set a bigger size for the buffer, but when i set a big value (1048576) , the execution of the command 
succeeds but the target does not respond anymore and needs to be reboot. I have set it to one value less than the value 
set on net.bpf.maxbufsize(1048576) and still fails.. 

Can you let me know  "absolute limit" ?

sysctl -w net.inet.udp.recvspace=1048576
net.inet.udp.recvspace: 41600 -> 1048576

The command returns successfully , but the target just hangs and we had to reboot the target.


After some binary search, we find that the pain is between  262144 and 131072 i guess. 131072 works and 262144 hangs.. I
 dont know if there is some other parameter that we need to set that is related to this..So, i wonder the limit for this
 property.