Data Communication and Host Modes
Rev 3.0B Feb.08
57
remote
IP/port
until
no
data
is
sent
or
received
for
the
time
interval
defined
in
the
UDP
auto
answer
time
‐
out
(S83).
During
this
session,
packets
from
other
IP/port
addresses
will
be
rejected,
unless
*UALL
is
set.
Whether
or
not
an
incoming
packet
will
cause
the
modem
to
enter
a
UDP
session
is
always
dependent
on
the
S53
and
AIP
settings.
The
Normal
UDP
Mode
(MD3)
can
be
combined
with
UDP
auto
answer
to
cause
the
incoming
serial
data
to
be
sent
in
UDP
packets
(instead
of
being
treated
as
AT
commands),
while
allowing
sessions
to
be
established
from
different
UDP
sources.
A
UDP
session
will
be
initiated
either
by
incoming
serial
data
or
by
an
incoming
UDP
packet.
The
session,
started
by
either
method,
will
be
terminated
when
no
data
has
been
sent
or
received
for
the
S82
period.
Once
the
session
termi
‐
nates,
another
may
be
initiated
by
either
means.
When
idle,
after
the
time
‐
out
has
occurred,
the
modem
is
in
AT
command
mode
on
the
serial
port,
and
any
valid
AT
command
may
be
entered
during
this
time.
Tip: It is best to ensure the idle time-outs for TCP and UDP are never
0 if you're going to be using auto-answer, or either PAD mode. In
those circumstances, you will want the modem to close the socket if
the connection goes idle for too long, particularly if the other side
doesn’t normally close the connection.
When
the
session
is
initiated
by
serial
data,
the
new
session
will
be
established
using
the
destination
address
specified
in
S53.
The
S53
setting
can
be
changed
if
the
connect
to
last
UDP
setting
(*UDPLAST=1)
is
set.
The
address
in
S53
will
be
updated
to
reflect
the
address
of
the
last
session
initiated
by
an
incoming
UDP
packet.
So
that
when
new
data
is
received
over
the
host
serial
port
while
in
the
idle
state,
a
session
will
be
re
‐
established
with
the
last
address.
(This
behavior
is
the
same
as
the
previous
Hybrid2
(MD6)
mode).
Tip: TCP auto answer (S0) may also be set simultaneously with UDP
auto answer. Then, when in the idle state, the modem will accept
either a TCP or UDP incoming packet, and enter a TCP or UDP
session as appropriate.
Reliable UDP
Reliable
UDP
adds
a
simple
protocol
on
top
of
UDP
to
provide
reliable
delivery
of
data.
When
data
is
received
from
the
host
serial
port,
a
2
byte
header
is
added
to
the
data,
containing
a
message
type
and
a
sequence
number.
The
Raven
will
continue
to
send
this
data
(buffering
any
received
data
in
the
meantime)
