[Discuss-gnuradio] "file sink" problem when I use GRC

Hi,all:

I use 2 USRP N210 and 2 PC to transmit a file. And implement it by GRC.

PC1（transmitter）:

PC2（receiver）:

In my PC1(transmitter) I have a file and the content is "hello world". I think the PC2(receiver) should receive the file and save it in the path which I define.

But when I implemented the GRC example I saw the "hello world" output in the console, but did't write into the file in PC2.The file in PC2 still blank.

This  "files transmit " example I had seen on the youtube and it can be successful obtain the data and save to the receiver. So I don't where I went wrong. 

Thanks,

Ke