The tcp_receive node

This node is used to receive data from a tcp socket. There are two modes it can operate in:

• Connect: If ip is set to a valid hostname or ip address, the node will connect to that peer and then just waits for incoming data.
• Listen: Without ip, the node will just open a tcp listen port and waits for a connection from outside to receive data.

Data - Parser

When we define a parser module, incoming data can be parsed to faxe's internal data-format with it.

If no parser is defined, incoming data will be set as is to the field given with the as paramenter.

If both parser and as are not given, the node assumes, that incoming data has JSON format and will try to decode it into faxe's internal format.

Packet size

Data is expected with a defined packet size.

packet can be: 1 | 2 | 4 and defaults to 2. Packets consist of a header specifying the number of bytes in the packet, followed by that number of bytes. The header length can be one, two, or four bytes, and containing an unsigned integer in big-endian byte order.

`Length_Header:16/integer, Data:{Length_Header}/binary`

Since 0.19.19: packet now can also have the value 'line', if this is given, data from the socket will be treated as separated by newline characters (\n, \r\n).

---

If the changed option is given, the node will only emit on changed values (crc32 checksum comparison).

The tcp listener is protected against flooding with the {active, once} inet option.

Examples

|tcp_recv() 
.port(9745) 
.packet(4) 

Sets up a tcp listen socket on port 9745 and awaits an incoming connection. It uses a 4-byte length header to determine packet boundaries and will try to json-decode incoming data.

---

def parser = 'parser_robot_plc_v1'

|tcp_recv()
.ip('212.14.149.8')
.port(9715)
.parser(parser)
.as('data')

---

|tcp_recv()
.ip('212.14.149.8')
.port(9715) 
.packet(4)
.as('data.raw')

Parameters

Parameter	Description	Default
ip( string )	ip or hostname for the tcp peer	undefined
port( integer )	port number
packet( integer or 'line' )	packet length/type	2
parser( string )	name of parser to use for data conversion	undefined
as( string )	name of the field for parsed data	undefined
changed( is_set )	whether to check for changed data	false (not set)