Listens for RELP messages being sent to a given port over TCP. Each message will be acknowledged after successfully writing the message to a FlowFile. Each FlowFile will contain data portion of one or more RELP frames. In the case where the RELP frames contain syslog messages, the output of this processor can be sent to a ParseSyslog processor for further processing.


listen, relp, tcp, logs


In the list below, the names of required properties appear in bold. Any other properties (not in bold) are considered optional. The table also indicates any default values, and whether a property supports the NiFi Expression Language.

Display NameAPI NameDefault ValueAllowable ValuesDescription
Local Network InterfaceLocal Network InterfaceThe name of a local network interface to be used to restrict listening to a specific LAN.
Supports Expression Language: true (will be evaluated using variable registry only)
PortPortThe port to listen on for communication.
Supports Expression Language: true (will be evaluated using variable registry only)
Receive Buffer SizeReceive Buffer Size65507 BThe size of each buffer used to receive messages. Adjust this value appropriately based on the expected size of the incoming messages.
Max Size of Message QueueMax Size of Message Queue10000The maximum size of the internal queue used to buffer messages being transferred from the underlying channel to the processor. Setting this value higher allows more messages to be buffered in memory during surges of incoming messages, but increases the total memory used by the processor during these surges.
Max Size of Socket BufferMax Size of Socket Buffer1 MBThe maximum size of the socket buffer that should be used. This is a suggestion to the Operating System to indicate how big the socket buffer should be. If this value is set too low, the buffer may fill up before the data can be read, and incoming data will be dropped.
Character SetCharacter SetUTF-8Specifies the character set of the received data.
Max Number of Worker ThreadsMax Number of TCP Connections2The maximum number of worker threads available for servicing TCP connections.
Max Batch SizeMax Batch Size1The maximum number of messages to add to a single FlowFile. If multiple messages are available, they will be concatenated along with the <Message Delimiter> up to this configured maximum number of messages
Batching Message DelimiterMessage Delimiter\nSpecifies the delimiter to place between messages when multiple messages are bundled together (see <Max Batch Size> property).
SSL Context ServiceSSL Context ServiceController Service API:
Implementation: StandardRestrictedSSLContextService
The Controller Service to use in order to obtain an SSL Context. If this property is set, messages will be received over a secure connection.
Client AuthClient AuthREQUIRED
  • WANT
  • NONE
The client authentication policy to use for the SSL Context. Only used if an SSL Context Service is provided.


successMessages received successfully will be sent out this relationship.

Reads Attributes:

None specified.

Writes Attributes:

relp.commandThe command of the RELP frames.
relp.senderThe sending host of the messages.
relp.portThe sending port the messages were received over.
relp.txnrThe transaction number of the message. Only included if <Batch Size> is 1.
mime.typeThe mime.type of the content which is text/plain

State management:

This component does not store state.


This component is not restricted.

Input requirement:

This component does not allow an incoming relationship.

System Resource Considerations:

None specified.

See Also: