I was just wondering how I can test an echo server. The conclusion was to send a lot of random data and compare sent and received data. The first part I managed by calling openssl tool included in Git for Windows distribution to generate about 1.8GB random text. To send all the generated data I used NetCat for Windows.
openssl rand -base64 10000000000 -out /z/random.txt cat /z/random.txt | nc 127.0.0.1 54443 > /z/received.txt