stops when transmitting halfway


I have tried to transmit and receive data bits using the files found in
python/digital. i ran both files on two separate pcs attached with a
usrp each.

I used the following commands to initialised the two programs:

python --freq 900M --bitrate 500k
python --freq 900M --bitrate 500k.

The transmission and receive started but paused with no other futher

The transmit side shows:
gr_fir_fff: using SSE

The receive side shows:
gr_fir_fff: using SSE

Was quite puzzled at why the transmission stopped halfway.

Any help is really appreciated! Thank you so much!Regards,Joreen