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Poseidon2 & Damocles2 network communication protocols

Poseidon2 & Damocles 2 connects DI detectors, temperature, humidity and other sensors to the Ethernet network. In following text, you will learn closely about individual communication interfaces, that can be used for communication with Poseidon. Here you will also find some links to interesting SW utility programs.

Data from Poseidon or Damocles units can be retrieved by several methods depending on type of applications. Modbus/TCP is designed for visualization in industry, SNMP for telecommunications and professional remote administration. You can use XML for simple applications.

The Poseidon unit communication - XML, Modbus over TCP, (Modbus/TCP0, SNMP Trap, SNMP, SMS GSM modem

Request/response type of communication

Request-response protocols are designed for periodical logging of values from all sensors . Poseidon is in TCP Server mode and waiting for request from supervising application.


WEB - HTML (WWW page)

The Poseidon WEB interfaceTemperature and sensors' states are displayed on a simple WWW page which is first loaded when accessing Poseidon using web browser. The page is reloaded every 5 to 30 seconds (see the Poseidon manual).

If some variable reaches the value that is set as ALARM value, this binary input or a thermometer is colored red.

Access to this WWW page is not restricted, it only writes values and there is also nothing to modify. The access can be restricted by IP address filtering.

Notice: On the other hand for access to the Flash Setup user name and password can be demanded. You can find this option in "General Setup" bookmark in FLASH Setup. In case you forget your password new configuration of the device to "Set to Default" over RS-232 Setup is necessary


HTTP - XML tags

XML tags, TCP/IP communicationThe values, monitored by measuring sensors are displayed in the defined .XML page (for example values.xml) and they can be read easily from XML tags by any application. It represents the most efficient way of retrieving data for Machine-to-Machine TCP/IP, because values from all sensors are stored in one file. XML entry is comprehensible for a man as well, process independent on SW platform and information can be retrieved even without a special software.

Note: We recommend using XML as the input interface for your SW applications.

Example of XML record for a thermal sensor:

<Name>TempSens1</Name> - sensor name
<Type>RS232</Type> - sensor type
<ID>T0</ID>  - identification
<Temper>15</Temper>  - actual temperature
<TempRange>05.0 - 35.0</TempRange>  - allowed temp. range
<Alarm>none</Alarm> - alarm state
<State>0</State>  - sensor state

Example of XML file with 4 sensors and XML format description in DTD and SCH file can be found in the utility package. For example the Poseidon model 1140 -

Notice: Majority of the Poseidon models contains two XML files which differ in range of commands. The smaller file (typically values.xml) is used for print-out of connected sensors state. The second file (typically setup.xml) contains full device configuration data and you can dump sensor values, names of sensors, their alarm state configuration and others using your SW application. If the setting of Poseidon allows it, you can change some parameters directly in this file.


Modbus over TCP

The Modbus is a communication protocol developed for measuring devices communicating over RS-485 or RS-232The Modbus is a communication protocol developed for measuring devices communicating over RS-485 or RS-232. The Modbus protocol allows sharing the variables' memory area over one of the physical interface, from measuring values for instance. Modbus/TCP represents the extension of this protocol for Ethernet communication.

Easy implementation into visualization systems for industrial professions is advantageous.

Mapping the variables of the Modbus/TCP protocol
Analogue values
Address I/O Type Function Units Description
100 Input Int 4   Actual amount of installed sensors (and configured in Setup)
101-10x Input Int 4 0,1°C (K, F) Actual value of the sensor 1 - x where x means value of the address 100, units can be set in Flash Setup mode
Binary values
100 - 102 Input bit 2 0 - open, 1 - close Actual value of a binary input
200 Input bit 1 0 - open, 1 - close Actual value of a binary output
200 Output bit 5 0 - open, 1 - close Binary output value configuration

From the Modbus's standpoint, Poseidon operates as a TCP Server on port 502 (Modbus standard). Communications run on the addresses defined by the Modbus/TCP protocol. For more information, see .

Schedule of individual parameters mapping can be found in the Poseidon manual.


SNMP - question / answer

The SNMP (Simple Network Management Protocol, MIB (Management Information Base) table) - SNMP Traps SNMP (Simple Network Management Protocol) is suitable for primary system information exchange using short packets sent via UDP/IP.

Individual variables are organized and described in so-called MIB (Management Information Base) table, which can be used for any device. The table is distributed as a separate .mib file that can be downloaded to Poseidon from our web pages or found on the supplied CD.

SNMP is an asynchronous protocol based on the client/server model (here SNMP Client/SNMP Agent). This means that the supervisor (SNMP Client) queries Poseidon for the state of the individual values in MIB held in the Poseidon and SNMP Agent, implemented in Poseidon, responds.

SNMP protocol support is provided in many languages intended for creating dynamic WWW pages (e.g. PHP, ASP, Java, Perl, Python and others). Thanks to existing modules it is possible to allow access to reading or writing the data, provided by peripheral device to the system (e.g. a Poseidon), over the SNMP protocol quite quickly.

In classic communication mode, the communication proceeds in terms of queries and responses. The variables are defined by a numeric string that is described in the MIB table that also defines the meanings of the individual variables, format and names. If you know the hierarchy (numeric string – e. g. „.“ – state of binary input 3) for a specific value, you don’t need the MIB table.

Basic terms:

  • MIB table (Management Information Base) .mib file is a text-based file, describing individual variables supported by the device. It contains variables' addresses, their name, description and numeric format.
  • OID (Object Identification) is an identifier of the variable in the variables’ chart. It is represented by a long number, defining the variable’s position within the variable tree structure.

Some programs do not support MIB files for working with SNMP. With these programs, you must enter the OID strings manually. The strings can be found in the MIB table, but to save you looking there, we provide a summary of several variables, their OID in Poseidon manual.


Event alarm type of communication

For unrepeated notice of beginning and end of alarm status, different type of protocols than for periodical logging is necessary. Poseidon reacts to events automatically and notice is sent to one or more recipients according to the configuration.

  • Poseidon processes Alarms as a state value,it also notices beginning and end of the Alarm state. Details can be found in manual for Poseidon.
  • The Poseidon unit support hysteresis for all sensor values..For Alarm status all measuring of continuous values use so called Hysteresis - belt of insensibility. Hysteresis is designed to prevent from many fake alarms in case the value oscillates over alarm value. Details in manual.
  • Following protocols for Alarm notification may not be supported with all Poseidon models. Basic information can be found on Poseidon family page, detailed table with list of supported protocols and individual models can be found on Poseidon product overview page.



Email (SMTP)

The Poseidon - Email over SNMPIf sending of an Email is allowed as a reaction to Alarm, Poseidon (Damocles) sends email directly or via supervising program. It is standard email, where recipient, subject and some parts of the message can be set.

TLS is secured connection with the SMTP server.

Methods of sending the email

  • Email is sent via external program (ex. HWg trigger)
    On a local server, the program runs and via SNMP supervises the state of one or more Poseidon units. In case of Alarm status, the program sends notice via email
    • (+) Email is always logged by an independent authority
    • (+) Email format is programmable
    • (-)It is necessary to guarantee a running application where to send SNMP Traps from Poseidon units and transmit emails. This means to rely on:
      • the local server and its program
      • the connection server - Poseidon unit
      • the connection server - SMTP server
  • Email sent via external SMTP server
    Poseidon connects directly to set SMTP server and transmit email for sending.
    • (-) external SMTP server necessary
    • (+) SMTP server logs sent emails
    • Poseidon supports user name and password authorization
  • Email sent via Poseidon directly to recipient's server
    This method is advantageous if the SMTP server for sending emails from the Poseidon unit is not always accessible. The Poseidon unit sends email directly to recipient's SMTP server. Ideal in case you do not have SMTP server for sending emails.
    • (+) You do not need SMTP server
    • (-) Email can be deleted by the server, according to missing reverse MX record which can recipient verify. Necessary to test recipient.
    • Email is never logged
    • Poseidon needs to set the DNS server



SNMP traps (alarms)

SNMP Traps when Alarm to NMSIf any thermometer's value exceeds the defined range, the sensor will switch to the Alarm and reports this by sending SNMP Trap to the specified IP address.

The trap consists of two SNMP traps for increasing of security and compatibility with other systems.
The format of the packet is described in MIB table, the first packet contains information about Alarm beginning and the second packet contains information about sensor in alarm status.

The alarm is state value so that after alarm termination (for example temperature goes back to the defined range) another two SNMP Traps are transmitted.

The trap system was developed to speed up delivery of information about changes of state because in the classic SNMP mode - question/answer, the period between each query can last from miliseconds up to several hours. For input contacts it is possible to define sending Alarm at Opening /Closing or the alarm can be disabled completely.

Detailed description and a summary of SNMP Traps can be found in the MIB table. The Poseidon manual contains enhanced description.



SMS (external GSM modem)

gsm alarming over SMS throught external GSM modem The alarm status notification can be realized with redirecting the Email to SMS. Because of possible failure, an independent GSM modem can be connected directly to the Poseidon unit or to the server which supervises with several Poseidon units.

Methods of SMS sending

  • HWg-SMS-GW3: GSM gateway for text messages (SMS)
    HWg-SMS-GW3 is a SMS gateway for sending text message alarms over a LAN. Send SMS alarms from other HW group products and software through a single gateway and a single SIM. No software needed, works over a LAN at the Box-2-Box level.
  • SMS sent via GSM modem from server
    On a local server, a program runs and via SNMP supervises the state of one or more Poseidon units. In Alarm status it sends notice via SMS via GSM modem which is connected directly to the server.
    • (+) For more Poseidon units central point is advantageous for setting all parameters in one step
    • (+) Alarm is always logged by an independent authority, it can be sent to Email as well
    • (+) SMS format is programmable
    • (+) Via SMS request, you can verify the state of several connected Poseidon units and their sensors
    • (-) It is necessary to guarantee running application where to send SNMP Traps from Poseidon units and transmit SMS. This means to rely on:
      • The local server and its program
      • The connection of server - Poseidon unit
      • The GSM modem
  • SMS sent via GSM modem connected to Poseidon RS-232 port
    Poseidon and GSM modem constitute an independent system. This construction is very resistant in case of many types of failures. However, this reliability does not apply on the failure of the power supply and the GSM network.
    • (-) It requests GSM modem connected to each Poseidon
    • (-) Via SMS, Poseidon sends only basic information about Alarms, It is not possible to know the state
    • (+) Stable and on the network infrastructure independent solution


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