Square
One
User’s
Guide
Page
49
Forwarding
incoming
connections
Introduction
to
port
forwarding
Like
most
other
routers,
your
Square
One
Personal
Server
by
default
blocks
all
incoming
communication
attempts
from
outside
computers
to
computers
and
devices
on
the
server’s
local
network,
unless
the
incoming
communications
are
in
response
to
an
outgoing
request
from
the
same
computer.
(Outgoing
connections
are
not
blocked
at
all.)
For
example,
when
you
request
a
web
page
on
the
Internet
by
entering
a
URL
in
your
browser,
your
Personal
Server’s
built
‐
in
router
“remembers”
which
computer
made
the
outgoing
request
and
to
what
web
server
the
request
was
made.
Then,
when
the
web
server
sends
the
requested
page,
the
router
passes
the
incoming
data
on
to
the
requesting
computer.
If
a
computer
on
the
Internet
attempts
to
connect
to
a
local
computer
without
the
local
computer
having
initiated
communications
with
it,
the
router
normally
blocks
the
attempt.
This
is
to
protect
your
network
against
unwanted
intrusion.
There
may
be
times
when
you
want
specific
kinds
of
incoming
connections
to
be
permitted
through
to
your
network—to
not
be
blocked
by
the
router—even
if
they
are
not
in
response
to
an
outgoing
request.
One
example
involves
the
popular
peer
‐
to
‐
peer
file
‐
sharing
application,
eMule.
For
eMule
to
work
best,
other
computers
(peers)
on
the
eMule
network
must
be
able
to
connect
to
your
computer
running
eMule,
although
your
computer
does
not
initiate
communications
with
them.
Blocking
these
incoming
connections
causes
both
download
and
upload
speeds
in
eMule
to
be
reduced.
Port
forwarding
is
provided
by
the
router
as
a
way
to
accommodate
exceptions
to
the
general
policy
of
blocking
all
unsolicited
incoming
connections.
Port
forwarding
takes
advantage
of
the
fact
that,
for
any
given
Internet
application,
incoming
connections
are
almost
always
addressed
to
certain
specific
ports
on
the
destination
computer.
For
example,
requests
for
web
pages
are
almost
always
addressed
to
the
web
server’s
port
80,
and
the
web
server
is
said
to
“listen”
for
incoming
connections
on
that
port.
(It
may
be
useful
to
think
of
ports
as
being
like
individual
mailboxes
in
an
apartment
building,
and
think
of
the
building
as
being
like
a
computer.
For
a
letter
to
reach
its
destination,
you
must
specify
both
the
building’s
address
and
the
apartment
number.)
If
you
want
to
allow
incoming
connections
to
a
program
running
on
your
computer—eMule,
for
example—configure
the
router
to
forward
connections
on
the
port
(or
ports)
on
which
eMule
