sing-box/docs/configuration/shared/udp-over-tcp.md

!!! warning ""

It's a proprietary protocol created by SagerNet, not part of shadowsocks.

The UDP over TCP protocol is used to transmit UDP packets in TCP.

Structure

{
  "enabled": true,
  "version": 2
}

!!! info ""

The structure can be replaced with a boolean value when the version is not specified.

Fields

enabled

Enable the UDP over TCP protocol.

version

The protocol version, 1 or 2.

2 is used by default.

Application support

Project	UoT v1	UoT v2
sing-box	v0 (2022/08/11)	v1.2-beta9
Clash.Meta	v1.12.0 (2022/07/02)	v1.14.3 (2023/03/31)
Shadowrocket	v2.2.12 (2022/08/13)	/

Protocol details

Protocol version 1

The client requests the magic address to the upper layer proxy protocol to indicate the request: sp.udp-over-tcp.arpa

Stream format

ATYP	address	port	length	data
u8	variable	u16be	u16be	variable

ATYP / address / port: Uses the SOCKS address format, but with different address types:

ATYP	Address type
0x00	IPv4 Address
0x01	IPv6 Address
0x02	Domain Name

Protocol version 2

Protocol version 2 uses a new magic address: sp.v2.udp-over-tcp.arpa

Request format

isConnect	ATYP	address	port
u8	u8	variable	u16be

isConnect: Set to 1 to indicates that the stream uses the connect format, 0 to disable.

ATYP / address / port: Request destination, uses the SOCKS address format.

Connect stream format

length	data
u16be	variable

Non-connect stream format

As the same as the stream format in protocol version 1.