The Acknowledge Message has the additional fields shown in Table 70.

Table 70 – OPC UA Connection Protocol Acknowledge Message

Name

Type

Description

ProtocolVersion

UInt32

A protocol version supported by the Server that is less than or equal to the protocol version requested in the Hello Message.

If the Client accepts the protocol version it shall ensure that it sends Messages that conform to this version.

The ProtocolVersion for this version of the standard is 0.

ReceiveBufferSize

UInt32

The largest MessageChunk that the sender can receive.

This value shall not be larger than the SendBufferSize requested in the Hello Message.

Shall be at least 8 192 bytes if the SendBufferSize requested in the Hello Message is >= 8 192 bytes. Shall be at least 1 024 bytes otherwise.

SendBufferSize

UInt32

The largest MessageChunk that the sender will send.

This value shall not be larger than the ReceiveBufferSize requested in the Hello Message.

Shall be at least 8 192 bytes if the ReceiveBufferSize requested in the Hello Message is >= 8 192 bytes. Shall be at least 1 024 bytes otherwise.

MaxMessageSize

UInt32

The maximum size for any request Message.

If a request Message exceeds this value the Client shall report a Bad_ResponseTooLarge error to the application. If MessageChunks have already been sent the Client shall also abort the Message as described in 6.7.3.

The Message size is calculated using the unencrypted Message body.

A value of zero indicates that the Server has no limit.

MaxChunkCount

UInt32

The maximum number of chunks in any request Message.

The Client shall abort the Message with a Bad_RequestTooLarge StatusCode if a request Message exceeds this value.

The mechanism for aborting Messages is described fully in 6.7.3.

A value of zero indicates that the Server has no limit.