Relay Mode Configurations

Configuration file example

Example of client mode:

mode=client
kcp=regular1
inbound_bandwidth=500M
outbound_bandwidth=50M
listen_port=59000
destination_port=3000-3010
destination_address=123.45.67.89
encryption_password=qwerty1234
encryption_algorithm=AES-GCM

Example of relay mode:

mode=relay

[listener]
kcp=regular1
inbound_bandwidth=300M
outbound_bandwidth=300M
listen_port=3000-3010
encryption_password=qwerty1234
encryption_algorithm=AES-GCM

[forwarder]
kcp=regular2
inbound_bandwidth=300M
outbound_bandwidth=300MM
destination_port=13000-13010
destination_address=87.65.43.21
encryption_password=qwerty1234
encryption_algorithm=AES-OCB
udp_timeout=10

Example of server mode:

mode=server
kcp=regular2
inbound_bandwidth=1G
outbound_bandwidth=1G
listen_port=13000-13010
destination_port=59000
destination_address=::1
encryption_password=qwerty1234
encryption_algorithm=AES-OCB

As you can see, the KCP settings and encryption options for the client and server are different.

That's right, you only need to correctly configure the channels on both sides of the relay station, and the relay node will re-encrypt when forwarding.

Process:

sequenceDiagram
    participant User's Application
    participant KCP Client
    participant KCP Relay
    participant KCP Server
    participant Server's Application
    User's Application->>KCP Client: Application Data
    Note over KCP Client: destination_port=3000-3010
    KCP Client->>KCP Relay: KCP Client Data
    KCP Client-->>KCP Relay: kcp=regular1<br/>AES-GCM
    Note over KCP Relay: [listener]<br/>listen_port=3000-3010<br/>#10;<br/>[forwarder]<br>destination_port=13000-13010
    KCP Relay->>KCP Server: KCP Client Data
    KCP Relay-->>KCP Server: kcp=regular2<br/>AES-OCB
    Note over KCP Server: listen_port=13000-13010
    KCP Server->>Server's Application: Application Data
    Server's Application->>KCP Server: Response Data
    KCP Server->>KCP Relay: KCP Server Data
    KCP Server-->>KCP Relay: kcp=regular2<br/>AES-OCB
    KCP Relay->>KCP Client: KCP Server Data
    KCP Relay-->>KCP Client: kcp=regular1<br/>AES-GCM
    KCP Client->>User's Application: Response Data

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Shareable options for Configuration Files

The following configuration options can be used outside [listener] and [forwarder] sections:

• kcp
• kcp_rcvwnd
• kcp_sndwnd
• outbound_bandwidth
• inbound_bandwidth
• encryption_password
• encryption_algorithm
• udp_timeout
• keep_alive
• ipv4_only=1

If these options appear outside of sections label, they override all corresponding values inside the section label. Among them, ipv4_only=1 is a special case, it is only covered when ipv4_only=1, and it is not covered when ipv4_only=0.

Because ipv4_only=0 means to use the default setting, that is, dual-stack mode.

For example, you can write:

mode=relay
kcp=fast1
outbound_bandwidth=300M
inbound_bandwidth=300M
encryption_password=qwerty1234
encryption_algorithm=AES-GCM

[listener]
listen_port=3000-3010

[forwarder]
destination_port=13000-13010
destination_address=127.0.0.1

If the KCP settings of the entire link are the same, it is really convenient to do so.

Notes

If you need to configure udp_timeout yourself, please ensure that the udp_timeout of the relay node is greater than or equal to the udp_timeout value of the server and client to avoid prematurely clearing the forwarding link.

About the Section Tags

When configuring relay mode, it is necessary to clearly write the section labels of the two nodes - [listener] and [forwarder], which cannot be ignored.