TCP Binding

Documentation of the TCP & UDP binding Bundle

Introduction

The TCP part of the binding has a built-in mechanism to keep connections to remote hosts alive, and will reset connections at regular intervals to overcome the limitation of "stalled" connections or remote hosts.

The TCP & UDP binding bundle acts as a network client, and not as a server. It will thus not accept any incoming connections, and thus is to be used with remote ends that act as servers.

For installation of the binding, please see Wiki page Bindings.

Generic Item Binding Configuration

In order to bind an item to a remote host:port, you need to provide configuration settings. The easiest way to do so is to add some binding information in your item file (in the folder configurations/items`). The syntax for the TCP & UDP binding configuration string is explained here:

Note: The examples here below are for the TCP protocol. UDP binding configuration are exactly the same, one only has to substitute "tcp=" with "udp="

The format of the binding configuration is simple and looks like this:

tcp="<direction>[<command>:<ip address>:<port>:<transformationrule>], <direction>[<command>:<ip address>:<port>:<transformationrule>], ..."

where <direction> is one of the following values:

• < - for inbound-triggered communication, whereby the openHAB runtime will act as a server and listen for incoming connections from the specified <ip address>:<port>

• • for outbound-triggered communication, whereby the openHAB runtime will act as a client and establish an outbound connection to the specified <ip address>:<port>

where <command> is the openHAB command. For String Items <command>: can be omitted

where <ip address> is the hostname or ip address in dotted notation of the remote host

and where <transformationrule> that will be applied to the <command> received, before the resulting string is to be sent to the remote host. For String Items the received value of the Item will be passed on to the <transformationrule>. When data is received from the remote host, then the Item will be updated with the <command> in so far that the result of the <transformationrule> applied on the incoming data is valid for the given Item. String items will be updated "as is" using the result of the <transformationrule>.

##Configuration Parameters

The TCP and UDP bindings are highly configurable through the openhab.cfg . The following parameters can be set (substitute "tcp=" with "udp=" for the UDP binding): The indicated values are the default values used by either binding

tcp:refreshinterval=250 - This is a mandatory field in order to start up the binding - Refresh interval for the polling thread, can be used to manage oh Host CPU Load

tcp:port=25001 - This is a mandatory field when inbound communication (<direction> equals <) are used - Port to listen on for incoming connections.

tcp:addressmask=true - Allow masks in ip:port addressing, e.g. 192.168.0.1:** etc

tcp:reconnectron='0 0 0 ** * ?' - Cron-like string to reconnect remote ends, e.g for unstable connection or remote ends

tcp:retryinterval=5 - Interval between reconnection attempts when recovering from a communication error, in seconds

tcp:queue=true - Queue data whilst recovering from a connection problem (TCP only)

tcp:buffersize=1024 - Maximum buffer size whilst reading incoming data

tcp:preamble='' - Pre-amble that will be put in front of data being sent

tcp:postamble='\r\n' - Post-amble that will be appended to data being sent

tcp:blocking=false - Perform all write/read (send/receive) operations in a blocking mode, e.g. the binding will wait for a reply from the remote end after data has been sent

tcp:timeout=3000 - Timeout, in milliseconds, to wait for a reply when initiating a blocking write/read operation

tcp:updatewithresponse=true - Update the status of Items using the response received from the remote end (if the remote end sends replies to commands)

The parameters here below influence the way the binding will multiplex data over TCP and UDP connections

tcp:itemsharedconnections=true - Share connections within the Item binding configurations

tcp:bindingsharedconnections=true - Share connections between Item binding configurations

tcp:directionssharedconnections=false - Share connections between inbound and outbound connections

##Examples

Here are some examples of valid binding configuration strings:

tcp=">[ON:192.168.0.1:3000:'MAP(my.device.map)')], >[OFF:192.168.0.1:3000:'MAP(my.device.map)']" // for a Switch Item where values are converted using the my.device.map
tcp="<[192.168.0.2:3000:'REGEX((.*))']" // for a String Item that captures some state of a remote device that connects to openHAB