Avaya VTCPD Features (Software Release 2.1 on MPS 2.1) User Manual download pdf (Page 46)

VTCPD Features User Manual

Page 46 P0602483 Ver: 03.41

VTCPD Features User Manual

Message Format

Two message formats are available - fixed length, and variable length. Fixed length

messages have a predefined length, and most variable length messages use a special

character (or a string) to specify the end of the message. However, the variable length

message with a fixed byte message header message format uses a predefined header to

specify message length.

Message formats can be specified by:

• -f l:lenfld [:pos [:hdrlen] ] option for binary length fields.

• -f a:lenfld [:pos [:hdrlen] ] option for ASCII length fields.

The following is important information regarding the use of these options:

• If both fixed-length and variable-length messages must be processed, then two

instances of the daemon must be used, each started with a different value for

the -n <name> parameter.

• VTCPD adds a message header or a delimiter to a string received from an

application. The application should not include a message header or a

delimiter with the message sent to the daemon.

The length field contains the length of the message body. However, if options -f L or

-f A are specified instead of -f l or -f a, the length field contains the total

message length (message header and body). The position is counted from 1 (default);

hdrlen defaults to lenfld + pos - 1.

The position of the message length information is predefined in the header and the

system goes to the specified Length Field to obtain the message length specification.

For example, the Position of the message Length Field can be defined as beginning on

the fourth character of the header and the Length Field can be defined as being six

characters long. The system proceeds to the fourth character, and reads the next six

characters to obtain the message length.

Message Format

Message Lengths

Format Description

fixed length The message contains a fixed number of bytes.

variable length Variable length message delimited using a special character or a string.

Variable length message with a fixed byte message header that defines

the message length.

Position

Length Field

Header

Message

Message Body

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 113 114

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Avaya VTCPD Features (Software Release 2.1 on MPS 2.1) User Manual Page 46