0: **Server** knows no peers
1: **Sender** connects, sends _ANNOUNCE_, waits for **Receiver**, **Sender** is ready to send data
1.1 **Server** knows 1 peer - **Sender**
2: **Receiver** connects, sends _ANNOUNCE_, waits for **Sender**, **Receiver** is ready to receive data
2.2 **Server** knows 2 peers
2.3 **Server** relays _ANNOUNCE_ to **Sender**
3: **Sender** receives _ANNOUNCE_
3.1 **Sender** sends _DATA_ to **Server**
3.2 **Server** relays _DATA_ from **Sender** to **Receiver**
3.3 **Receiver** saves DATA
4: File transfer is complete, **Sender** sends _COMPLETE_ to **Server**
4.1: **Server** relays _COMPLETE_ to **Receiver**
4.2: **Receiver** semds _COMPLETE_ to **Server**
5.1: **Server** removes peers
5.2 **Sender** exits
5.3 **Receiver** exits