Siemens S7 API reference

Siemens S7 connector programming specifications

FairCom provides specific API actions to configure the Siemens S7 connector. Be sure to enable the Siemens S7 service before requesting data from a Siemens S7 server.

Note A connector is a bridge between a device/software and an integration table. 

 

Request examples

Note The FairCom createInput JSON action is used to define the specifics of a connector device and the desired data.

Minimal

{
  "action": "createInput",
  "params": {
    "inputName": "mySiemensS7",
    "serviceName": "siemensS7",
    "thingName": "PLC 74", 
    "settings": {
      "ipAddress": "127.0.0.1",
      "rack": 0,
      "slot": 2,
      "dataCollectionIntervalMilliseconds": 5000,
      "propertyMapList": [
        {
          "propertyPath": "flag1",
          "memoryArea": "db",
          "dataBlockNumber": 1,
          "offset": 0,
          "dataType": "word"
        }
      ]
    },
    "tableName": "siemensS7Table"
  },
  "authToken": "replaceWithAuthTokenFromCreateSession"
}
 
 

Maximal

{
  "api": "hub",
  "action": "createInput",
  "params": {
    "inputName": "mysiemensS7",
    "serviceName": "siemensS7",
    "thingName": "PLC 74",
    "dataPersistenceStrategy": "onChange", 
    "dataCollectionIntervalMilliseconds": 500,
    "immediatelyCollectDataOnStart": true,
    "dataCollectionBufferCount": 2,
    "settings": {
      "ipAddress": "127.0.0.1",
      "rack": 0,
      "slot": 2,
      "packageSize": 500,
      "propertyMapList": [
        {
          "propertyPath": "status",  //Deprecated
          "memoryArea": "db",
          "dataBlockNumber": 1,
          "offset": 0,
          "amount": 1,
          "dataType": "bit",
          "bitPosition": 3
        },
        {
          "tagName": "nerrors",
          "memoryArea": "db",
          "dataBlockNumber": 1,
          "offset": 2,
          "amount": 3,
          "dataType": "doubleword"
        },
        {
          "tagId": 18,
          "memoryArea": "db",
          "dataBlockNumber": 1,
          "offset": 20,
          "amount": 2,
          "dataType": "real"
        }
      ]
    },
    "databaseName": "ctreeSQL",
    "ownerName": "admin",
    "tableName": "siemensS7Table",
    "retentionPolicy": "autoPurge",
    "retentionPeriod": 30,
    "retentionUnit": "day",
    "metadata": {
    }
  },
  "authToken": "replaceWithAuthTokenFromCreateSession"
}
 
 

 

Response examples

A response to a request is "0" when successful. A non-zero value response indicates an error occurred.

Success

{
    "result": {},
    "requestId": "00000007",
    "errorCode": 0,
    "errorMessage": ""
}
 
 

 

Properties

Request properties ("params")

Property Description Default Type Limits (inclusive)

databaseName

The "databaseName" property specifies the database that contains an object, such as a table or code package. If it is set to null or is omitted, it defaults to the default database of the JSON Action session, see "createSession" and the "defaultDatabaseName" property. 

You specify this property when you want to use a different database instead of the default. Your session's account must have the appropriate privileges to access the code package.

This property is useful because objects, such as tables and code packages, can have the same name in multiple databases. This feature allows you to create multiple environments in the same server and reuse the same JSON actions in each environment. For example, you can create "dev", "test", "stage", and "prod" databases on the same server and use the "defaultDatabaseName" or "databaseName" properties to specify the desired environment.

It is an error to set "databaseName" to the empty string "".

If no default database is specified during "createSession", the server sets the "defaultDatabaseName" to the "defaultDatabaseName" value specified in the services.json file.

 Defaults to the session's "defaultDatabaseName" property string 1 to 64 bytes

dataCollectionBufferCount

The "dataCollectionBufferCount" property specifies the number of times the collector retrieves and caches data from the device before writing the data to the integration table.

This option combines multiple data collection events and inserts them into the integration table as one MQTT message.

If this value is more than 1, the connector converts each set of collected data into a JSON object and adds the object to an array inside a JSON document. When the count is reached, the connector writes the JSON document to the source_payload field of a record it inserts into the integration table.

 Optional with default of 1 integer 1 to 65535

dataCollectionIntervalMilliseconds

The "dataCollectionIntervalMilliseconds" property schedules the connector to collect data periodically using the specified number of milliseconds. 

 Optional with default of 10000 (10 seconds). integer 0 and negative values are invalid.

dataPersistenceStrategy

The "dataPersistenceStrategy" property controls when a connector writes collected data to a record in the input table specified by "tableName". 

  • The "onSchedule" setting causes the connector to persist each collected value, which occurs on the schedule set by the "dataCollectionIntervalMilliseconds" property. This setting is useful for continuously collecting device data for trend analysis and machine learning.
  • The "onChange" setting causes the connector to collect data on the schedule set by the "dataCollectionIntervalMilliseconds" property, but it only persists data when it changes. This allows the connector to detect and store data changes as events, such as alerts and status updates. This setting greatly reduces data storage for infrequently changing telemetry, such as changes to a temperature sensor.

Note The connector misses events when its data collection schedule is not frequent enough to see data changes. Thus, the "onChange" setting makes a polling protocol, such as Modbus, behave like a push protocol, but it is not a push protocol like MQTT.

 Optional with default of "onSchedule" string

"onSchedule"

"onChange"

description

 The "description" property assigns a description to a connector. Optional with default of "" string 1 to 512 bytes

enabled

 The "enabled" property turns on or off an input or output connector. Thus, it pauses or starts data collection or delivery. Optional with default of true Boolean

true

false

enabledFilter

 The "enabledFilter" property returns input connections that are enabled or not. Omit or set to null to match all connections. Optional with default of null Boolean

true

false

immediatelyCollectDataOnStart

The "immediatelyCollectDataOnStart" property controls how a connector first collects data after being started.

  • When true, it immediately collects and stores data and thereafter collects data according to the strategy specified in "dataPersistenceStrategy". In other words, it ignores the "dataPersistenceStrategy" for the initial data collection event and unconditionally stores the first set of data it collects. This setting allows subscribers to receive an initial data collection message each time the server or connector starts, which is useful for systems that display live status information.
  • When false, which is the default, it collects data according to the strategy specified in "dataPersistenceStrategy". For example, when the "dataPersistenceStrategy" is "onChange", the connector collects data on a schedule and persists it only when the data changes - even after a restart.
 Optional with default of false Boolean

true

false

inputName

The "inputName" property specifies the unique name of an input. A FairCom generated name follows the pattern "Input #n from <pluginName> to <databaseName>.<ownerName>.<tableName>".

"params": {
    "inputName": "modbusTCP",
    "serviceName": "modbus"
}

Required - No default value

 string 1 to 100 bytes

metadata

 The "metadata" property contains user-defined properties that add keywords and tags about the code package. The server indexes this field with a full-text index so you can search for any word or phrase to find code packages. Optional with default of {} object 0 or more key/value pairs

ownerName

The "ownerName" property specifies the account that owns an object, such as a table or code package. See "createSession" and the "defaultOwnerName" property for more details. 

You specify this property when you want to use a different account instead of the default. Your session's account must have the appropriate privileges to access the code package. 

This property is useful because objects, such as tables and code packages, can have the same name in the same database as long as different accounts own each object. This feature allows you to create duplicate objects for different users on the same server and reuse the same JSON actions on those objects. For example, an administrator can copy objects from a production environment to her account so she can troubleshoot an issue using the same JSON actions, JavaScript, and SQL code.

It is an error to set "ownerName" to the empty string "".

If no default owner is specified during "createSession", the server sets the "defaultOwnerName" to the "defaultOwnerName" value specified in the services.json file.

 Optional with default of the session's "defaultOwnerName" property string 1 to 64 bytes

purpose

 The "purpose" property specifies the purpose of the thing. You can use it for fast partial lookups and filtering.  Optional with default of "unknown"  string

1 to 64 bytes

Values are managed in the Label API with the group "faircom/edge/purpose".

retentionPeriod

The "retentionPeriod" property specifies how many units of data to retain. It refers to the unit of time specified by the "retentionUnit" property. For more details, see "retentionPeriod".

Optional with default of 30

 integer 1 to 100

retentionPolicy

The "retentionPolicy" property controls how messages are persisted. 

If not specified, the default found in the services.json file is used. Initially, it is "autoPurge".

 

retentionPolicy values:
  • "autoPurge"
    • This is the default. It is automatically applied when a new topic is created. It is preferred because it allows FairCom's servers to automatically remove messages that are older than the retention time. This helps ensure message data does not consume all storage space. It also minimizes storage costs and speeds up data access. The server partitions a table into multiple files so it can efficiently delete expired files.
  • "neverPurge"
    • This stores messages on disk and never removes them. This is useful when you need the entire history of the message stream. If message velocity is high, this can consume all storage space and cause an outage. The server creates a non-partitioned table, which is slightly faster than a partitioned table because it stores all records in one file.

Optional with default of "autoPurge"

 string

"autoPurge"

"neverPurge"

retentionUnit

The "retentionUnit" property specifies a unit of time that the server will use to purge expired messages. For example, if you want a week's worth of messages to be purged once a week, set "retentionUnit" to "week". This property is optional.

If not specified, the default found in the services.json file is used. Initially, it is "week". 

  • This property is used in concert with "retentionPeriod" to determine retention time.
  • "retentionUnit" values:
    • "minute"
    • "hour"
    • "day"
    • "week"
    • "month"
    • "year"
    • "forever"

Note 

  • For best performance, set the "retentionUnit" to a value that keeps "retentionPeriod" between 5 and 30. 
  • When you set "retentionUnit" property to "forever" the server will not purge messages. This setting is the same as setting "retentionPolicy" to "neverPurge".
  • The "retentionUnit" and "retentionPeriod" properties are used only when the "retentionPolicy" is set to "autoPurge".

Optional with default of "day"

string

"minute"

"hour"

"day"

"week"

"month"

"year"

runningFilter

 The "runningFilter" property returns input connections that are running or not. Omit or set to null to match all connections. Optional with default of null Boolean

true

false

serviceName

The "serviceName" property contains the name of a FairCom input or output service. 

See the "params" topic of each specific service for the requirements of this property.

The following services are available as of the V5 release:
  • "MODBUS"
  • "SIEMENSUDT2JSON"
  • "OPCUA"

Note The SQL, JSON RPC, and REST services can automatically query any integration table in FairCom's servers without requiring configuration.

MQTT always represents both input and output services. This is because once a topic is created and assigned to an integration table, any MQTT client can publish messages to it and subscribe to those messages.

 Required - No default value string 1 to 64 bytes

settings

The "settings" property contains properties that are specific for each connector type. Settings for Modbus are different than settings for OPC UA, and so forth. See the API reference "params" property of each connector for details of the "settings" property for that connector.

 Optional with default of {} object

See these pages for connector specific properties:

Allen-Bradley "params"

Modbus "params"

OPC UA "settings"

Siemens S7 "params"

settings

.dataCollectionIntervalMilliseconds

The "dataCollectionIntervalMilliseconds" property schedules the connector to collect data periodically using the specified number of milliseconds. 

 Optional with default of 10000 (10 seconds). integer 0 and negative values are invalid.

settings

.ipAddress

 The "ipAddress" property specifies the PLC/Equipment IPV4 Address. Required - No default value string A valid IP address

settings

.packageSize

The "packageSize" property specifies the package size in bytes used to communicate with the PLC. 

Higher numbers allow the connector to retrieve more data in fewer requests. If not specified, the PLD PDU size is used.

 Optional with default between 240 and 960 integer 240 to 960

settings

.propertyMapList

 The "propertyMapList" property specifies which data the connector requests and where to put it in the generated JSON. Required - No default value array of objects

zero or more objects containing zero or more of the following properties:

"amount"

"bitPosition"

"dataBlockNumber"

"dataType"

"memoryArea"

"offset"

"propertyPath"

settings

propertyMapList

.amount

The "amount" property specifies the number of consecutive "dataType" values the connector retrieves.

The connector retrieves 3 one-byte values when "amount" is 3 and "dataType" is "byte".  

The connector retrieves 2 four-byte values when "amount" is 2 and "dataType" is "real".

If "dataType" is "bit", "amount" must be 1 because the connector retrieves one 8-bit byte for each bit. See "bitPosition" below.

 Optional with default of 1 integer 1 to 65535

settings

propertyMapList

.bitPosition

 If "dataType":"bit", "bitPosition" defines which of the eight zero-based bits to read from the byte the connector retrieves. Optional with default of 0 integer 0 to 7

settings

propertyMapList

.dataBlockNumber

The "dataBlockNumber" property specifies the number of the Data Block memory area where the connector retrieves data.

It is ignored unless "memoryArea":"db".

 Required if "memoryArea": "db" integer 1 to 65535

settings

propertyMapList

.dataType

The "dataType" property specifies the data type of memory retrieved by the connector.

If "memoryArea":"ct", "dataType" must be "counter". 

If "memoryArea":"tm", "dataType" must be "timer".

 Required - No default value string
  • "bit" - inside a byte
  • "byte" - 8-bit integer
  • "ubyte" - unsigned 8-bit integer
  • "word" - 16-bit integer
  • "uword" - unsigned 16-bit integer
  • "doubleword" - 32-bit integer
  • "udoubleword" - unsigned 32-bit integer
  • "real" - 32-bit float
  • "counter" - 16-bit integer
  • "timer" - 16-bit integer

settings

propertyMapList

.memoryArea

 The "memoryArea" property specifies the type of memory area where the connector retrieves data. Required - No default value string
  • "pe" - Process Inputs
  • "pa" - Process Outputs
  • "mk" - Flags "Merkers" 
  • "db" - Data Block
  • "ct" - Counters
  • "tm" - Timers

settings

propertyMapList

.offset

 The "offset" property specifies the offset to the starting byte in the memory area where the connector retrieves data. Required - No default value integer 0 to 4294967296

settings

propertyMapList

.propertyPath

 The "propertyPath" property specifies the JSON path in the JSON document where the connector puts the data it collects. It is mutually exclusive with the "tagName" and "tagId" properties. Required - No default value string JSON path

settings

propertyMapList

.tagId

 The "tagId" property associates a tag with a value being collected by a connector. It is mutually exclusive with the "tagName" and "propertyPath" properties. See tagId for more details. Conditional - No default value integer If present, it must contain the ID of an existing tag, which is an integer from 0 to 9223372036854770000.
Note FairCom recommends using this property instead of "propertyPath".

settings

propertyMapList

.tagName

 The "tagName" property associates a tag with a value being collected by a connector. It is mutually exclusive with the "tagId" and "propertyPath" properties. See tagName for more details.  Conditional - No default value string

If present, it must contain the name of an existing tag. 

Note FairCom recommends using this property instead of "propertyPath".

settings

.rack

 The "rack" property specifies the PLC Rack number. Required - No default value integer 0 to 7

settings

.slot

 The "slot" property specifies the PLC Slot number. Required - No default value integer 1 to 31

status

 The "status" property assigns an active or inactive status to a thing. An inactive status is like a soft delete.  Optional with default of "active" string enum

"active"

"inactive"

tableName

The "tableName" property contains the unique, user-defined name of a table.

The table name must start with an upper or lowercase letter, must not contain special characters other than underscore "_", and can include a mix of upper-lower case characters, but are treated as case-insensitive.

 

"params": {
  "tableName": "ctreeTable"
}
 Required - No default value string 1 to 64 bytes

thingId

 The "thingId" property associates a connector with a device or software application. It is mutually exclusive with the "thingName" property. See thingId for more details.  Optional with default of null integer If present, it must contain the ID of an existing thing, which is an integer form 0 to 9223372036854770000.

thingName

 The "thingName" property associates a connector with a device or software application. It is mutually exclusive with the "thingId" property. See thingName for more details. Optional with default of null string 1 to 64 bytes

 

Response properties ("result")

Property Description Type Limits (inclusive)

data

The "data" property contains a response message. Its contents are defined by the action. It is an empty array when no results are available. The following is an example of the data property from a code package action.

  "result": {
    "data": [
      {
        "codeId": 6,
        "databaseName": "faircom",
        "ownerName": "admin",
        "codeName": "convertAndCategorizeTemperature",
        "codeVersion": 1,
        "clonedCodeId": 1,
        "codeStatus": "active",
        "codeLanguage": "javascript",
        "serviceName": "javascript",
        "codeType": "module",
        "description": "optional new description",
        "metadata": {},
        "createdBy": "ADMIN",
        "createdOn": "2025-08-25T21:48:38.109",
        "updatedBy": "ADMIN",
        "updatedOn": "2025-08-25T21:48:38.109",
        "comment": "Cloned from convertTemperature",
        "codeFormat": "utf8"
      },
    ]
 array of objects The action determines its contents.

data

.enabled


The "enabled" property is true when a connector is allowed to connect to a device. It is false when a connector will not attempt to connect to the device.

 

 boolean true
false

data

.running

 The "running" property is true when an input connector is collecting data or an output connector is delivering data; otherwise, it is false. A disabled connector will never be running. An enabled connector may or may not be running. Boolean

true

false

data

.settings

The "settings" property contains properties that are specific for each connector type. Settings for Modbus are different than settings for OPC UA, and so forth. See the API reference "params" property of each connector for details of the "settings" property for that connector.

 object

See these pages for connector specific properties:

Allen-Bradley "params"

Modbus "params"

OPC UA "settings"

Siemens S7 "params"

data

settings

.propertyMapList

 The "propertyMapList" property specifies which data the connector requests and where to put it in the generated JSON. array of objects

See these pages for connector specific properties:

Allen-Bradley "params"

Modbus "params"

OPC UA "settings"

Siemens S7 "params"

data

settings

propertyMapList

.propertyPath

 The "propertyPath" property specifies the JSON path in the JSON document where the connector puts the data it collects. It is mutually exclusive with the "tagName" and "tagId" properties. string JSON path

data

settings

propertyMapList

.tagId

 The "tagId" property associates a tag with a value being collected by a connector. It is mutually exclusive with the "tagName" and "propertyPath" properties. See tagId for more details. integer If present, it must contain the ID of an existing tag, which is an integer from 0 to 9223372036854770000.
Note FairCom recommends using this property instead of "propertyPath".

data

settings

propertyMapList

.tagName

 The "tagName" property associates a tag with a value being collected by a connector. It is mutually exclusive with the "tagId" and "propertyPath" properties. See tagName for more details.  string

If present, it must contain the name of an existing tag. 

Note FairCom recommends using this property instead of "propertyPath".

data

.stopCode

 The "stopCode" property is 0 when the connector is successfully connected to its device or software; otherwise, it is non-zero. integer -2147483648 to 2147483647

data

.stopReason

 The "stopReason" property is "" when the input connector is collecting data; otherwise, it is a non-empty string. string 0 to 256 bytes

data

.thingId

 The "thingId" property associates a connector with a device or software application. It is mutually exclusive with the "thingName" property. See thingId for more details.  integer If present, it must contain the ID of an existing thing, which is an integer form 0 to 9223372036854770000.

data

.thingName

 The "thingName" property associates a connector with a device or software application. It is mutually exclusive with the "thingId" property. See thingName for more details. string 1 to 64 bytes

 

 
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