Neo4j Bolt Handshake Protocol Introduced

The Bolt Handshake Protocol Specification defines the protocol that allows a server and client to initiate a connection in Bolt Protocol.

This article provides an overview of the Bolt Handshake Protocol.

Handshake Workflow

The fundamental process for a client to establish a connection with a server is illustrated below:

First, the client declares its intent to initiate a connection using the Bolt Protocol by sending a fixed 4-byte message:

C: 60 60 B0 17

Next, the client sends four supported versions of the Bolt Protocol, each represented as a 32-bit unsigned integer in big-endian format.

For example, in the diagram above, the client supports the following four versions:

• v4.2: 00 00 02 04
• v4.1: 00 00 01 04
• v4.0: 00 00 00 04
• v3.x: 00 00 00 03

The client transmits these versions as the following bit sequence:

C: 00 00 02 04 00 00 01 04 00 00 00 04 00 00 00 03

The server selects a suitable Bolt Protocol version from the list and returns it to the client. Suppose the server chooses v4.1:

S: 00 00 01 04

Summary

To summarize, the following bit sequences are exchanged in total. The entire process requires three round-trips:

C: 60 60 B0 17
C: 00 00 02 04 00 00 01 04 00 00 00 04 00 00 00 03
S: 00 00 01 04

This concludes the overview of the Binary Handshake Protocol.