Steps

1. Open pcap file in wireshark.
2. Notice the communication between src and destination. Select any packet.
3. Right click > Follow > TCP Stream.
4. Paste data into tcpstr1.txt file.
5. Run python sol.py

Original writeup (https://github.com/s-nirali/squarectf-2017/tree/master/sniffed-off-the-wire).