Attributes to Configure in the Comm-Port Point

Attribute Name Description
transmission mode Specifies the communication mode as either ASCII (zero) or RTU (one).
socket info

Specifies the host and service name to use when making a socket connection. The entry to use is specified in the "socket index" attribute. This table contains the following:

Field Number Field Name DE Type Possible Values
0 host name rtBYTES16 (see below)
1 service name rtBYTES12 (see below)

Where:

Field Name Description
host name Valid host name in either IP format (e.g. 1.2.3.4) or hostname from /etc/hosts.
service name

Valid service name from /etc/services. The socket number specified should be specified using tcp (eg. modbus 502/tcp).

[caution] The Modbus TCP documentation specifies that the reserved socket number 502 should be used.
socket index Specifies the index into the "socket info" table of the entry to use.
max data length The request(s) will be formatted such that the number of data bytes returned from the RTU will not exceed this number. This value is only read on startup. The minimum value for this is four. If the value is less than this minimum, it will be silently set to the minimum.
debug device UNIX

The device file where debug information is to be printed. The full path must be provided; for example "/dev/ptyqf". In addition to a device file, the following key words are recognized: "stdout" and "stderr"; which send debug information to the specified file pointer.

[warning] If a pseudo-terminal device is to be used, specify the master device; otherwise the driver will be hung on the open waiting for the master side of the pseudo-terminal to be opened.

 

[caution] If a pseudo-terminal device is used, the scan task must be started before any process tries to open the slave device; otherwise no debug information will be printed.
Windows

This specifies a "named pipe" that will be created on the server machine. Client applications can then make connections to this "named pipe" to receive debug information. A separate thread is created to handle each client. There is a maximum of six client connections allowed. Additional clients trying to connect will fail.

Since this is a "named pipe", clients can connect from other machines on the network.

See the tesserNet Scan Debug Utilities for freely distributable client applications.

[warning] Depending on the network connection speed, some debug data may be lost. Tests here, show that for a full 10 Mbit/sec connection, no data is lost.