You may get an error like below, when you are transferring data from one system to another system using scp

scp -P 22 -r root@ /home/.

total-inventory-cost.php.svn-base 100% 3758     3.7KB/s   00:00  
filename.txt          1%  224KB   0.0KB/s - stalled -
filename2.txt         1%  224KB   0.0KB/s - stalled

I have faced three types of problems,

>> Network Connection
>> Check Firewall setting
>> SCP attempt to grab much bandwidth

Sometimes the scp getting to grab as much bandwidth or file transfer delay, It's possible to solve this error set the bandwidth  limit 1 MB/seconds : 8192 Kbit/second

For example,
scp  -l 8192  -P  22   Source    Destination

Now, files can transferring to another system  up to 1 MB/second