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Overview

The YSviaversion module provides version adaptation functionality, allowing clients running different YSFlight versions to connect to the server by translating login packets to match the server’s expected version.

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Functions

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genViaVersion()

def genViaVersion(username: str, finalVersion: int) -> bytes
Generates a modified login packet that ports a player’s connection to a different YSFlight version.
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username
str
required
The player’s username (maximum 16 characters)
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finalVersion
int
required
The target YSFlight version number to port to (e.g., 20181124 for YSFlight version 20181124)
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return
bytes
A binary packet containing:
  • Packet size (4 bytes): Always 24
  • Packet type (4 bytes): Always 1 (LOGON)
  • Username (16 bytes): ASCII-encoded username with null padding
  • Version (4 bytes): The target version number

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Packet Structure

The generated packet follows this binary format: 
[size: 4 bytes][type: 4 bytes][username: 16 bytes][version: 4 bytes]
  • Size: Total payload size (24 bytes)
  • Type: Packet type identifier (1 for LOGON)
  • Username: 16-byte field with ASCII characters followed by null padding
  • Version: Target version as unsigned 32-bit integer

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Example

from lib import YSviaversion

# Port player to YSFlight version 20181124
username = "Player1"
target_version = 20181124

packet = YSviaversion.genViaVersion(username, target_version)
# Returns binary packet ready to send

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Usage in Proxy

Version adaptation is automatically applied when a player connects with a different version than the server expects: 
# From proxy.py:171-176
if packet_type == "FSNETCMD_LOGON":
    decode = FSNETCMD_LOGON(packet)
    player.login(decode)
    
    if player.version != YSF_VERSION and VIA_VERSION:
        info(f"ViaVersion enabled: Porting {player.username} from {player.version} to {YSF_VERSION}")
        message_to_client.append(YSchat.message(f"Porting you to YSFlight {YSF_VERSION}"))
        message_to_client.append(YSchat.message(f"This is currently Experimental"))
        data = YSviaversion.genViaVersion(player.username, YSF_VERSION)

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Configuration

Version adaptation is controlled by configuration variables: 
# config.py
VIA_VERSION = True  # Enable/disable version adaptation
YSF_VERSION = 20181124  # Target server version

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Notes

  • Usernames longer than 16 characters will be truncated
  • Usernames shorter than 16 characters are padded with null bytes (\x00)
  • Each character is encoded as ASCII bytes
  • The feature is experimental and may not support all version differences
  • Players receive chat notifications when version porting is applied
  • The original login packet is replaced with the generated version-adapted packet

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Limitations

  • Only modifies the login packet version field
  • Does not translate protocol differences between versions
  • May not work for significantly different YSFlight versions
  • Experimental feature requiring testing with various version combinations

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