Rockwell Automation EtherNet/IP Original Instructions

Application Technique

Original Instructions

EtherNet/IP Socket Interface

Summary of Changes

This publication contains the following new or updated information. This list includes substantive updates only and is not intended to reflect all changes.

Topic

Page

Added ControlLogix® 5580 controllers, GuardLogix® 5580 controllers,

CompactLogix™ 5380 controllers, Compact GuardLogix 5380 controllers, Throughout

Compact GuardLogix 5370 controllers, CompactLogix 5480 controllers,

Added Disable the Socket Object With a MSG Instruction.

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2	Rockwell Automation Publication ENET-AT002D-EN-P - October 2020

Table of Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

	Chapter 1
Socket Interface Architecture	Socket Interface Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 8
	Number and Type of Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	8
	Typical Sequence of Transactions for a TCP Client . . . . . . . . . .	10
	Typical Sequence of Transactions for a TCP Server. . . . . . . . . . .	11
	Typical Sequence of Transactions for UDP without
	OpenConnection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
	Typical Sequence of Transactions for UDP with
	OpenConnection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13
	Communicate with the Socket Object Via a MSG Instruction . . . .	14
	Service Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16
	MSG Instruction Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16
	Socket Instance Timeouts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	Disable the Socket Object With a MSG Instruction . . . . . . . . . . . . . .	18
	Programming Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20
	TCP Connection Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20
	ControlLogix Enhanced Redundancy . . . . . . . . . . . . . . . . . . . . . . .	20
	EtherNet/IP Module Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	21
	Change Controller Mode between Run and Program . . . . . . . . .	22
	Application Messages and TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	22
	Application Messages and Inhibited Modules . . . . . . . . . . . . . . . .	23
	Partial Reads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	23
	Partial Writes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	24
	Performance Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	25
	Chapter 2
Socket Object Services	Socket Create . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	28
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	28
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	29
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	29
	Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	29
	OpenConnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	30
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	30
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	31
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	31
	Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	31
	AcceptConnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	32
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	32
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	32
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	33
	Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	33
	ReadSocket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	34

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Table of Contents
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	34
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	35
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	35
	WriteSocket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	36
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	36
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	37
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	37
	DeleteSocket. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	38
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	38
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	38
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	38
	Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	38
	DeleteAllSockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	39
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	39
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	39
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	39
	Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	39
	ClearLog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	40
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	40
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	40
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	40
	JoinMulticastAddress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	41
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	41
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	42
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	42
	DropMulticastAddress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	42
	MSG Source Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	42
	MSG Source Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	43
	MSG Destination Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	43
	Chapter 3
Socket Attributes	Access Socket Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	45
	Socket Class Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	46
	Socket Instance Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	47
	Chapter 4
Troubleshoot Socket Applications	Diagnostic Webpages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	49
	Debugging Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	50
	Error Codes for Socket Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	51
	Knowledgebase Articles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	52
	Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	53

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Preface

Additional Resources

This publication describes the socket interface that you can use to program MSG instructions to communicate between a Logix 5000™ controller via an EtherNet/IP™ module and Ethernet devices that do not support the EtherNet/IP application protocol, such as barcode scanners, RFID readers, or other standard Ethernet devices.

These documents contain additional information concerning related products from Rockwell Automation.

Resource	Description
Ethernet Design Considerations Reference Manual,	Provides a general description of the EtherNet/IP protocol
publication ENET-RM002	and how to use an EtherNet/IP network.
Embedded Switch Technology Reference Architectures	Provides design recommendations for connecting device-
Reference Manual, publication ENET-RM003	level topologies to larger, switch networks comprised of
	Layer 2 access switches.
EtherNet/IP Network Devices User Manual, publication	Describes how you can use EtherNet/IP communication
ENET-UM006	modules with your Logix 5000 controller and
	communicate with various devices on the Ethernet
	network.
Industrial Automation Wiring and Grounding	Provides general guidelines for installing a Rockwell
Guidelines, publication 1770-4.1	Automation industrial system.
Product Certifications website rok.auto/certifications.	Provides declarations of conformity, certificates, and
	other certification details.

You can view or download publications at rok.auto/literature.

Rockwell Automation Publication ENET-AT002D-EN-P - October 2020

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Preface

Notes:

6	Rockwell Automation Publication ENET-AT002D-EN-P - October 2020

Chapter 1

Socket Interface Architecture

Topic	Page
Socket Interface Architecture	8
Communicate with the Socket Object Via a MSG Instruction	14
Service Timeouts	16
MSG Instruction Timeouts	16
Socket Instance Timeouts	17
Disable the Socket Object With a MSG Instruction	18
Programming Considerations	20
Performance Considerations	25

The socket interface lets a Logix 5000™ controller communicate via an EtherNet/IP™ module with Ethernet devices that do not support the EtherNet/IP application protocol. Such devices include barcode scanners, RFID readers, or other standard Ethernet devices.

Socket services are available with these modules:

•ControlLogix® 5580 and GuardLogix® 5580 controllers,

•CompactLogix™ 5380 and Compact GuardLogix 5380 controllers

•CompactLogix 5370 and Compact GuardLogix 5370 controllers

•CompactLogix 5480 controllers

•1756-EN2x, 1756-EN3TR, and 1756-EN4TR EtherNet/IP communication modules

•1756-EWEB and 1768-EWEB EtherNet/IP web server modules

IMPORTANT MicroLogix™ 1400 controllers also support socket capability, but the information in this document does not apply to those products. For details on those products, see the MicroLogix 1400 Programmable Controllers Reference Manual, publication 1766-RM001D.

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Chapter 1 Socket Interface Architecture

Before you use the socket interface, make sure that you are familiar with these concepts:

•Basic TCP/IP, UDP, and socket programming concepts

•How to write socket programs in a programming language, such as C or Visual Basic

•How to use diagnostic tools, such as a network sniffer

•The application protocols of the devices and applications with which the Logix 5000 controller communicates

•How to write ladder logic or Structured Text for a Logix 5000 controller

Socket Interface Architecture The socket interface is implemented via the socket object in the EtherNet/IP module. Logix 5000 controller programs communicate with the socket object

via MSG instructions. MSG requests to the socket object are similar to socket API calls in most computer operating systems. The socket object services let you open connections, accept incoming connections, send data, and receive data.

To communicate with another device, you must understand the application protocol of the device. The EtherNet/IP module has no application protocol knowledge. The module makes only the socket services available to programs in Logix 5000 controllers.

Number and Type of Sockets

Number of supported socket instances:

32 Socket Instances		20 Socket Instances
•	ControlLogix 5580 controllers	•	1756-EWEB EtherNet/IP web server module
•	GuardLogix 5580 controllers	•	1768-EWEB EtherNet/IP web server module

•CompactLogix 5480 controllers

•CompactLogix 5380 controllers

•Compact GuardLogix 5380 controllers

•CompactLogix 5370 controllers

•Compact GuardLogix 5370 controllers

•1756-EN2x EtherNet/IP communication modules

•1756-EN3TR EtherNet/IP communication module

•1756-EN4TR EtherNet/IP communication module

Each instance can be one of these types:

•UDP socket—Sends and receives UDP datagrams.

•TCP client socket—The Logix 5000 program initiates the connection.

•TCP server socket—Another device initiates the connection to the Logix 5000 program.

•TCP listen socket—Listens on a specified port number for incoming connections.

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Socket Interface Architecture	Chapter 1

These options are available for UDP and TCP send and receive services.

Type	Communication	Send (Write)	Receive (Read)
UDP	Unicast	Yes	Yes
	Multicast	Yes	Yes
	Broadcast	Yes	Yes
TCP	Unicast	Yes	Yes
	Multicast	—	—
	Broadcast	—	—

You must have a listen socket for each TCP port number that accepts connections. Multiple TCP server sockets can share a listen socket if the connections are made to the same port number.

You can partition the available socket instances between UDP and TCP sockets in these ways:

•Use all instances for client TCP connections.

•Use one instance to listen for incoming TCP connections and then accept the remaining connections from other devices.

•Perform both TCP client and server operations.

•Perform both TCP and UDP operations.

These socket services are available.

Socket Service	Socket Instance	Page
Socket Create	Server or client	28
OpenConnection	Client	30
AcceptConnection	• If you issue an AcceptConnection service, the instance is a listen type.	32
	• If the AcceptConnection service returns an instance as a result of an
	incoming connection request, the socket instance is a server type.
ReadSocket	Server or client	34
WriteSocket	Server or client	36
DeleteSocket	Server or client	38
DeleteAllSockets	Server or client	39
ClearLog	Server or client	40
JoinMulticastAddress	Server or client	41
DropMulticastAddress	Server or client	42

Once you open a connection on a client socket instance, you cannot use the same socket instance to accept incoming connections. Similarly, if you accept connections on a socket instance, you cannot then use the instance to open outgoing connections. This behavior is consistent with standard socket API behavior.

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Chapter 1 Socket Interface Architecture

Typical Sequence of Transactions for a TCP Client

The following diagram shows a typical sequence of socket interface transactions with the Logix 5000 controller that acts as a TCP client. Each transaction between the Logix 5000 controller and the EtherNet/IP module is a message (MSG) instruction.

This example shows the Logix 5000 controller sending data to a device, and then the device sending a response. This sequence of transactions is typical. Depending on the application protocol, the device could instead initiate sending data to the Logix 5000 controller once the connection is open.

Also, each write transaction does not require an application response or acknowledgment. The application protocol determines the exact sequence of application transactions.

Controller

Create Socket

Create Socket Response

Instance = 102

OpenConnection "192.168.1.11?Port=49200"

OpenConnection Response

Write Data = abc

Write Response

Read

Read Response Data = xyz

EtherNet/IP Module	Device
192.168.1.10	192.168.1.11

Open TCP

Connection

Data = abc

The response is returned to the controller as soon as the data is sent.

Data = xyz

Accept Connection

Receive Data

Send Data

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Socket Interface Architecture	Chapter 1

Typical Sequence of Transactions for a TCP Server

The following diagram shows a typical sequence of socket interface transactions with the Logix 5000 controller as a TCP server. Each transaction between the Logix 5000 controller and EtherNet/IP module is a MSG instruction.

The following is a typical sequence of transactions. The exact sequence of sending and receiving data depends on the application protocol.

Controller

EtherNet/IP Module

Device

192.168.1.10

192.168.1.11

Create Socket

Port = 49100

Create Socket Response

Instance = 102

AcceptConnection

Open Connection

Open TCP Connection

Port=49100

Send Data

AcceptConnection Response

Data = abc

Read

Read Response

Data = abc

Write

Data = xyz

Data = xyz

Receive Data

Write Response

The response is returned to the controller as soon as the data is sent.

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Chapter 1 Socket Interface Architecture

Typical Sequence of Transactions for UDP without OpenConnection

The following diagram shows a typical sequence of socket interface transactions for UDP communication without using the OpenConnection service to specify the destination address. In this case, the Logix 5000 controller specifies the destination for each datagram and receives the address from the sender along with each datagram it receives. Each transaction between the Logix 5000 controller and the EtherNet/IP module is a MSG instruction.

This example shows the Logix 5000 controller sending data to a device, and then the device sending a response. This sequence of transactions is atypical. Depending on the application protocol, the device could instead initiate sending data to the Logix 5000 controller. Also, each Write transaction does not require an application response or acknowledgment. The application protocol determines the exact sequence of application transactions.

Controller

Create Socket

Port=49100

Create Socket Response

Instance = 102

Write 192.168.1.11?Port=49200 Data = abc

Write Response

Read

Read Response 192.168.1.11?Port=49200 Data = xyz

EtherNet/IP Module	Device
192.168.1.10	192.168.1.11

Data = abc

The response is returned to the controller as soon as the data is sent.

Data = xyz

Receive Data from Port 49200

Send Data to 192.168.1.10, Port 49100

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Socket Interface Architecture	Chapter 1

Typical Sequence of Transactions for UDP with OpenConnection

The following diagram shows a typical sequence of socket interface transactions for UDP communication when using the OpenConnection service to specify the destination address. Each transaction between the Logix 5000 controller and the EtherNet/IP module is a MSG instruction.

The following is a typical sequence of transactions. The exact sequence of sending and receiving data depends on the application protocol.

Controller

Create Socket

Port=49100

Create Socket Response

Instance = 102

Open Connection 192.168.1.11?Port=49200

Open Connection Response

Write

Data = abc

Write Response

Read

Read Response 192.168.1.11?Port=49200 Data = xyz

EtherNet/IP Module	Device
192.168.1.10	192.168.1.11

Data = abc

The response is returned to the controller as soon as the data is sent.

Data = xyz

Receive Data from Port 49200

Send Data To

192.168.1.10, Port 49100

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Chapter 1 Socket Interface Architecture

Communicate with the Socket Object Via a MSG Instruction

In a Logix 5000 controller program, use a CIP™ Generic MSG instruction to request socket services.

IMPORTANT The MSG instruction must be sent to the EtherNet/IP module via backplane.

On the Configuration tab, configure the parameters as described in Table 1.

Table 1 - Configuration Tab

Field	Description
Message Type	Choose CIP Generic.
Service Type	Choose a socket service type. The software automatically completes the Service Code and Class
	fields.
	Choose Get Attributes Single or Set Attributes Single when getting or setting a Socket Object
	attribute. For more information, see Access Socket Attributes on page 45.
Service Code	Type the unique service code that corresponds to the socket service you chose in the Service Type
	field.
Class	Type 342 (hexadecimal) for the socket object.
Instance	Type one of these values:
	• 0 for Socket Create, Delete All Sockets, and ClearLog services
	• Instance number that is returned by Socket Create for other services
	Use a relay ladder instruction or Structured Text statement to move the returned instance
	number from a Socket Create service into the .Instance member of a MSG instruction.
Attribute	Type an attribute value only when getting or setting an attribute, but not when using other
	services.
Source Element	Choose the tag that contains the request parameters for the socket service. To define the request
	parameters, create a user-defined data type for the tag.
Source Length	Enter the length of the source element.
Destination	Choose the tag that contains the response data that is returned by the socket service. To define
Element	the response data, create a user-defined data type for the tag.

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Socket Interface Architecture	Chapter 1

On the Communication tab, configure the parameters that are described in

Table 2.

IMPORTANT If you are using the front Ethernet port on a controller, you must use unconnected MSG instructions.

Table 2 - Communication Tab

Field	Description
Path	Enter the communication path to the EtherNet/IP module. The module must be accessed via
	the backplane; you cannot access the module via the Ethernet port.
	• For all controllers and communication modules, the path is 1, x. Where x is the slot
	number of the communication module, or the slot number of a ControlLogix 5580
	controller if the front Ethernet port is used.
	• For all supported CompactLogix controllers, the slot is 0.
	• For all CompactLogix 5370, CompactLogix 5380, Compact GuardLogix 5380,
	CompactLogix 5480, ControlLogix 5580, and GuardLogix 5580 controllers with version
	28.11 or later, you can also use a path of ‘THIS’.
Large Connection	• When using the controller’s built in Ethernet port, large messages are supported by
	default (they are also unconnected messages).
	• When using an Ethernet module through the backplane, the Connected checkbox and
	the Large Connection checkbox must be selected to use large messages. A large
	connection is only available with connected MSG instructions. For information about
	how to use the Connected or Cache Connections options, refer to the Logix 5000
	Controllers Messages Programming Manual, publication 1756-PM012.
	• IMPORTANT: To use controller memory efficiently, use large connections only for
	ReadSocket or WriteSocket services that require more than the standard connection size,
	as shown in Table 3.

The maximum amount of data you can send or receive depends on how you configure the MSG instruction, as shown in Table 3. The size of the data excludes the parameters in the ReadSocket and WriteSocket services.

Table 3 - Maximum Packet Sizes

Service	Unconnected Size	Standard Connection Size	Large Connection Size
ReadSocket	484 bytes	484 bytes	3984 bytes
WriteSocket	462 bytes	472 bytes	3972 bytes

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Chapter 1 Socket Interface Architecture

Service Timeouts

If a MSG requests more than the maximum packet size (standard or large), the module can return a failure status and the MSG instruction can set the .ER bit:

•For TCP sockets, if the application data is larger than the maximum size, you can issue multiple ReadSocket or WriteSocket services to receive or send the entire application message.

•For UDP sockets, the size of application data cannot exceed the maximum sizes for the ReadSocket and WriteSocket services.

You must specify a timeout parameter in milliseconds for any service that does not always complete immediately, such as OpenConnection, AcceptConnection, ReadSocket, and WriteSocket services. The timeout tells the socket object the maximum amount of time to wait when attempting to complete the service. While waiting for the service to complete, the MSG instruction is enabled.

If the requested service does not complete before the timeout period expires, the socket object returns a response to the service request. See the service descriptions in Chapter 2 for the content of the response.

IMPORTANT Make the value of the service timeout parameter is shorter than the MSG instruction timeout. Otherwise, application data could be lost.

MSG Instruction Timeouts	The default MSG instruction timeout is 30 seconds. The maximum MSG
	timeout is approximately 35 minutes. Specify the MSG instruction timeout by
	setting the appropriate member of the MSG tag:
	• If the MSG is unconnected, set the UnconnectedTimeout member.
	• If the MSG is connected, set the ConnectionRate and
	TimeoutMultiplier member.
	The MSG timeout is determined by multiplying the ConnectionRate by the
	TimeoutMultiplier. A TimeoutMultiplier of 0 corresponds to multiplier of 4,
	1 corresponds to multiplier of 8, and so on.

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	Socket Interface Architecture Chapter 1
Socket Instance Timeouts	Each socket instance has an inactivity timeout with a default of 5 minutes. If a
	socket instance receives no service requests for the amount of time that is
	specified by the inactivity timeout, the socket instance is deleted. If you then
	try to use the socket instance, the MSG instruction receives the error class or
	instance not supported.
	You can change the timeout by setting the inactivity time-out attribute via the
	Set Attribute service. See Socket Instance Attributes on page 47.
	If you put the controller in Program mode and then back into Run mode
	before existing socket instances time out, you can receive errors when the
	program tries to create socket instances. Eventually the socket instances time
	out and you can create more instances.
	IMPORTANT Make sure that the inactivity timeout is longer than the longest interval
	between socket operations. If the inactivity timeout is too short, socket
	instances can time out and result in MSG instruction errors.

Rockwell Automation Publication ENET-AT002D-EN-P - October 2020

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