The socket client in a CometBFT or Tendermint Core node makes use of a communication protocol that we call the "Tendermint Socket Protocol" or TSP over the 4 connections between a node and the application.

This is an extremely simple request/response-based protocol that takes place over TCP. Each request or response message is protobuf-encoded, but has a length delimiter prefix that is encoded as a varint.

In the v0.34.x release series, this length delimiter prefix is encoded as a signed varint, using the binary.PutVarint method.

In the v0.37.x release series, this length delimiter prefix has changed to instead use an unsigned varint (using binary.PutUvarint). This change happened because:

1. It's more standard to use unsigned varints to represent lengths, as they can generally never be negative and there's no meaning associated with a negative length.
2. We already did this correctly in the P2P layer in the v0.34.x series, meaning that we had two different approaches to representing length delimiters in different parts of the system. This change harmonizes the approach.

We also chose not to make this change in the v0.34.x series because doing so would break everyone's interaction with their socket-based ABCI applications.