PowerLAN in real life

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I bought a PowerLan adaptor to be able to connect to my private “server” (aka Raspberry PI) from the other side of the house via WLAN. Connecting the RP via WiFi wasn’t an option: two far away from the signal, I’d need to install at least one additional repeater and then two RP are without wireless adaptor. The PowerLan adaptor supports up to 1.200 MB/s and let’s me connect 3 devices directly. I won’t even need to buy an additional switch. And 1.200 MB/s. In theory, this is FAST. In reality the setup is complicated. The two adaptors are in the opposite location of a not-so-small house, the electrical stuff and cables were installed some 40 years ago. Some things you can only test after investing, and when thinking about how to connect to my servers, PowerLan was the only viable choice.

The setup was easy: one PoweLan adaptor connects to the Internet router, the other connects the RPs. Both find them and establish a secure connection. The connection signal is green, indicating a good connection. Connection tests showed that it is working: ping, ssh, all fine. It was time to check the speed. The RP isn’t the fastes when it comes to file server duties, but back in Rio I had 11 MB/s for copying files in Windows. That was fast enough. How will it be now? Laptop connected to WiFi (that is already not so good, given the layout of the rooms) and PowerLan that needs to communicate through several meters. It’s a worst case setup. I do not expect much.

A way to measure the speed is using netcat, or nc. Available in Linux and Mac. Basically the idea is to send data from the laptop to the RP and measure how long it does take to send 1MB, 10MB or more. The RP will serve as the receiving part, the laptop will send the data.

RP / Linux

Start nc, let it listen on port 2222 and send all incoming data to /dev/null

nc -v -l 2222 > /dev/null

Laptop

Read data from /dev/null, pipe it to nc and let it send to the nc instance running on the RP

dd if=/dev/zero bs=1024k count=512 | nc -v 192.168.2.112 2222

bs tells dd how much to read (1MB here) and count how many times. In the above example 512 MB will be send. To send 1 MB only, use count=1, for 10MB use count=10.

Results

1 MB

dd if=/dev/zero bs=1024k count=1 | nc -v 192.168.2.112 2222
found 0 associations
found 1 connections:
     1: flags=82<CONNECTED,PREFERRED>
 outif en0
 src 192.168.2.108 port 55619
 dst 192.168.2.112 port 2222
 rank info not available
 TCP aux info available
Connection to 192.168.2.112 port 2222 [tcp/rockwell-csp2] succeeded!
1+0 records in
1+0 records out
1048576 bytes transferred in 1.423923 secs (736399 bytes/sec)

Result: 736399 bytes/sec => 0.7 MB/sec.

10 MB

dd if=/dev/zero bs=1024k count=10 | nc -v 192.168.2.112 2222
found 0 associations
found 1 connections:
     1: flags=82<CONNECTED,PREFERRED>
 outif en0
 src 192.168.2.108 port 55624
 dst 192.168.2.112 port 2222
 rank info not available TCP aux info available
Connection to 192.168.2.112 port 2222 [tcp/rockwell-csp2] succeeded!
10+0 records in
10+0 records out
10485760 bytes transferred in 9.997975 secs (1048788 bytes/sec)

 Result: 1048788 bytes/sec => 1 MB/sec.

100 MB

dd if=/dev/zero bs=1024k count=100 | nc -v 192.168.2.112 2222
found 0 associations
found 1 connections:
     1: flags=82<CONNECTED,PREFERRED>
 outif en0
 src 192.168.2.108 port 55781
 dst 192.168.2.112 port 2222
 rank info not available
 TCP aux info available
Connection to 192.168.2.112 port 2222 [tcp/rockwell-csp2] succeeded!
100+0 records in
100+0 records out
104857600 bytes transferred in 103.159005 secs (1016466 bytes/sec)

Result: 1016466 bytes/sec => 1 MB/sec

 

Overall, the result is slower than the 11 MB/sec what I had before in Rio, but both connected  to the same WLAN. Now, with and unfortunate setup, PowerLAN gives me 1MB, and a working connection. It’s fast enough for storing documents. For copying a 100GB VM image it’s too slow.

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