prudp: update some details on virtual ports

docs/prudp.md

@@ -259,26 +259,29 @@ The CONNECT acknowledgement packet contains a [Buffer] with the following data:
 | Uint32 | Response check value + 1 |
 
 ### Virtual ports
-When multiple PRUDP connections are made to the same address, NEX doesn't create a new socket for each connection. Instead, it uses a single socket to create multiple PRUDP connections. To distinguish between connections, each packet contains a source and destination port.
+When multiple PRUDP connections are made to the same address, NEX doesn't create a new socket for each connection. Instead, it uses a single socket to create multiple PRUDP connections. To distinguish between connections, each packet contains a source and destination "virtual port". A "virtual port" is made of 2 parts, a stream type and stream ID. The client and server stream types will always match, though their IDs may not. How these are encoded depends on the protocol version. Each stream may be configured differently. Aspects of the connection such as retransmission rates, the encryption and compression algorithms, etc, are all controlled by these streams.
 
-**V0 and V1**: The four most significant bits contain the stream type. The four least significant bits contain the port number. The client port is the highest unused port number ≤ 0xF.
+**V0 and V1**: The virtual port uses a single byte. The four most significant bits contain the stream type. The four least significant bits contain the stream ID. The client stream ID is the highest unused stream ID ≤ `0xF`.
 
-**Lite**: The port number now uses 8 bits instead of 4. The client port is the highest unused port number ≤ 0x1F. The stream types are stored in a separate byte.
+**Lite**: The source and destination stream IDs are now encoded using 2 separate bytes. The stream type is encoded in a 3rd byte. The four most significant bits contain the source type. The four least significant bits contain the destination type. The client stream ID is the highest unused stream ID ≤ `0x1F`.
 
-**Server port (3DS/Wii U)**: The authentication and secure server each have their own UDP server. The server port is always 1.
+**Server stream ID (3DS/Wii U)**: The authentication and secure server each have their own UDP server. The server stream ID is always 1.
 
-**Server port (Switch)**: A single websocket server handles both authentication and secure connections. The authentication server has server port 1, the secure server has server port 2.
+**Server stream ID (Switch)**: A single websocket server handles both authentication and secure connections. The authentication server has server stream ID 1, the secure server has server stream ID 2.
 
-The stream type is always RVSecure (0xA) in Nintendo games.
-
-| Stream type | Name             | Stream type | Name     |
-|-------------|------------------|-------------|----------|
-| 1           | DO               | 7           | NATEcho  |
-| 2           | RV               | 8           | Routing  |
-| 3           | OldRVSec         | 9           | Game     |
-| 4           | SBMGMT           | 10          | RVSecure |
-| 5           | NAT              | 11          | Relay    |
-| 6           | SessionDiscovery |             |          |
+| Stream type | Name             | Details                                                              |
+|-------------|------------------|----------------------------------------------------------------------|
+| 1           | DO               | Unknown purpose                                                      |
+| 2           | RV               | Unknown purpose                                                      |
+| 3           | OldRVSec         | Original "secure" stream type. Used by NEX 1 and QRV clients         |
+| 4           | SBMGMT           | Unknown purpose                                                      |
+| 5           | NAT              | Unknown purpose                                                      |
+| 6           | SessionDiscovery | Unknown purpose                                                      |
+| 7           | NATEcho          | Unknown purpose                                                      |
+| 8           | Routing          | Unknown purpose. Not seen in non-NEX titles                          |
+| 9           | Game             | Unknown purpose. Not seen in non-NEX titles                          |
+| 10          | RVSecure         | New "secure" stream type. Used by NEX 2+. Not seen in non-NEX titles |
+| 11          | Relay            | Unknown purpose. Not seen in non-NEX titles                          |
 
 ### Type and flags
 This field takes up two bytes in the packet header and is encoded like this: `(flags << 4) | type`.