Avaya VTCPD Features (Software Release 2.1 on MPS 2.1) User Manual download pdf (Page 104)

VTCPD Features User Manual

Page 104 P0602483 Ver: 03.41

VTCPD Features User Manual

To simplify development of the host side processes sample code is included to deal

with network messaging. The source can be found in the

$ASEHOME/etc/vtcpd.host.sample file.

Fault Tolerance

Daemon Backup

A simple way to automatically restart the daemon in case of a crash is to invoke the

VTCPD using the following script:

#!/bin/csh

while (1)

vtcpd -v mpsname -l ...# Keep it in foreground

end # Will be reached only if

# vtcpd crashes

Monitoring Host Connections

If a host process dies, the kernel on the host machine notifies the VTCPD, which will,

in turn, send a condition hostdown to the applications. However the VTCPD will

not be notified if the entire host machine crashes or if the LAN connection is broken.

To detect this situation, the VTCPD should query the host periodically with a ping

command, declaring that it is down if no replies arrive in specified time.

Pinging the Host from the VTCPD

To query the host with a ping command, the timeout period must be specified by the

option -T timeout (in seconds). By default (and if the -h option is enabled) the ping

message is sent every three seconds which can be changed by the second part of -T

option: -T 30:10 generates ping message each 10 seconds with total timeout of 30

seconds.

It is also necessary to declare the format of the ping message by the

-h length[:string] option. For message formats using delimiters (-f d:ch)

or length headers (-f l:#) the length of the ping message may equal to zero (in

which case only the header or delimiter is shipped to the host. The string part of the

option -h is ignored). For fixed length format the length of the ping message can not

be zero though it may be smaller then the length of the message specified by -f len

option.

If the string part is not specified, the ping message is filled with ASCII '0'. If the string

contains exactly one character, the message will be filled with this character: -h4 and -

h4:0 and -h4:0000 are equivalent.

To specify an unprintable character, the hexadecimal representation (0xXX) should be

used. For example: -h 4:0x00 defines the ping message of 4 binary zeroes.

If the length of the string (each hexadecimal representation is counted for one

character) is greater then one, it should be exactly equal to the specified length: -h

4:A0x410x42B represents AABB message.

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Avaya VTCPD Features (Software Release 2.1 on MPS 2.1) User Manual Page 104