Using the Network Command String block

Network configuration

Once the Network Command String block is added to a Tesira layout, the Properties window allows entry of the destination's network parameters:

Refer to the documentation for the target device for the correct settings to apply in this section:

• The Protocol type TCP/UDP should be pre-defined or configurable depending on the device you intend to communicate with.
• The Server Address is the target IP or hostname of the 3rd party network device the block will be communicating with. Note that DNS must be supported on the network for the hostname resolution to occur.
• The Remote Port is the target port at the defined Server Address target IP that will be used.
  • In this screen capture, port 2202 has been pre-defined by the device manufacturer for communications.
  • Note that port 23 is the default as it is the default port for Telnet communications. References are available that define common ports and protocols for TCP/UDP.
• Auto Connect, when enabled, will attempt connection or reconnection every 3 seconds until successful.
• Connection Sequence (formerly Expected List) is a definable list that will be used to open communications with the target device once the network connection is active. The user defines the strings Expected from the target device followed by the appropriate Response strings. Once configured, the block will behave as follows:
  • IF Expected string1 is received, THEN Response string1 will be sent. IF Expected string2 is received, THEN Response string2 will be sent.
  • This Connection Sequence behaves in a very linear or serial manner.

Functional Configuration

Now that the Network Command String (NCS) block has been added to the file and configured with the proper network connection information, the block can be opened for functional configuration. Double-click on the block to open it.

1. The Command String Edit button allows the user to define command strings to be sent from the Tesira device.
2. The buttons in the Command Id column allow the strings to be sent manually.
3. The Input numbers align with the logic input nodes on the top of the NCS block. When a logic high is received on a logic input, the associated Command String will be sent.
4. The Expected Response section allows the user to define character strings that, when matched, will trigger an associated Command Id String and/or an associated Logic Output. More in-depth details will be covered below.
5. The Connection Log displays the character strings sent and received by Tesira. These are only visible while connected to a live system.

Response string pattern matching

Response String Patterns can be comprised of ordinary characters, hexadecimal escapes (a tilde character followed by two hexadecimal digits), question mark and asterisk. The following table describes the valid Response String Patterns.

When the NCS block receives input from the remote device, it attempts to match the received data (including any previously received but unmatched data already in the input buffer) against each of the Response Patterns, in order (i.e. first-match, not longest-match.)

1. When the first part of the input matches a pattern, the block removes the matching bytes from the input, then sends the selected Command String (if any) and pulses the selected Logic Output (if any).  Any unmatched bytes remain in the receive buffer for future matches.
2. When the entire input matches the initial portion of any pattern, but not the complete pattern, the block waits indefinitely for additional input.
3. If the input cannot match any pattern, the block discards the first byte of the input and tries again to match the remaining input.

Note that both the order and content of the patterns are important.  The following guidelines are recommended:

1. Response Patterns should start with a definite character or at least a definite count of characters.  Response Patterns starting with “*” or “?*” can cause the block to quit responding while it waits for additional input.
2. Response patterns should explicitly include trailing New Line (~0A), Carriage Return (~0D) or CR-LF (~0D~0A).
3. Response patterns cannot end with an asterisk  (*).