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sfecho.txt
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SFECHO(1) SFECHO(1)
NNAAMMEE
sfecho - Speak Freely remote echo server
SSYYNNOOPPSSIISS
ssffeecchhoo [ --dduu ] [ --pp_p_o_r_t ] [ --vv_t_i_m_e_o_u_t ]
DDEESSCCRRIIPPTTIIOONN
ssffeecchhoo is a server program which receives sound from re-
mote hosts in the same manner as ssffssppeeaakkeerr, but instead of
playing sound on the workstation's audio output, buffers
it in memory for ten seconds and then retransmits it to
the sending host. This allows remote users, even those
with half-duplex audio hardware, to experiment with dif-
ferent compression and encryption modes to optimise end-
to-end performance without tying up a person on the other
end of the connection.
ssffeecchhoo can echo sound in RTP and VAT protocols as well as
Speak Freely's native protocol. To permit this, messages
on both the specified port and the next higher numbered
port are monitored, queued, and retransmitted.
An echo server can invite connections by publishing its
existence on one or more directory servers. See the
``Look Who's Listening'' section in the ssffssppeeaakkeerr manual
page for details on how to set the environment variables.
OOPPTTIIOONNSS
--dd Enables debug output from ssffeecchhoo.
--pp_p_o_r_t Causes ssffeecchhoo to listen on the specified port num-
ber instead of the default port specified by ``IN-
TERNET_PORT'' in the MMaakkeeffiillee. To comply with the
RTP standard, the port specified should have an
even number; the next higher numbered port is used
for RTCP control messages.
--uu Prints how-to-call information.
--vv_t_i_m_e_o_u_t
When ssffeecchhoo receives a packet from a host it hasn't
heard from in _t_i_m_e_o_u_t seconds, it will attempt to
find the host name and print a message on standard
error noting the new connection and what compres-
sion mode is being used. If the host name can't be
found, the numeric IP address is given. After
_t_i_m_e_o_u_t seconds of inactivity a message is issued
indicating the host is idle. If no _t_i_m_e_o_u_t is
specified, 180 seconds is used.
BBUUGGSS
If ssffeecchhoo runs out of memory to buffer sound awaiting re-
transmission, packets are discarded without warning.
8 APR 1996 1
SFECHO(1) SFECHO(1)
By default, ssffeecchhoo listens on Internet port number 2074,
the same as ssffssppeeaakkeerr, and hence cannot run at the same
time on the same machine as ssffssppeeaakkeerr. You can specify a
different port for ssffeecchhoo with the --pp option, but many
users have difficulty connecting to servers with nonstan-
dard port numbers, so this isn't a terribly good idea for
public servers. If your server is intended primarily to
echo messages in RTP protocol, you may want to specify
port 5004, the default port for RTP specified in RFC
1890. Many VAT compatible applications default to port
3456.
AACCKKNNOOWWLLEEDDGGEEMMEENNTTSS
The implementation of MD5 message-digest algorithm is
based on a public domain version written by Colin Plumb in
1993. The algorithm is due to Ron Rivest. The algorithm
is described in Internet RFC 1321.
SSEEEE AALLSSOO
ssffssppeeaakkeerr(1)
AAUUTTHHOORR
John Walker
WWW: http://www.fourmilab.ch/
All modules of SSppeeaakk FFrreeeellyy developed by me are in the
public domain. See the rreeaaddmmee and/or ccooppyyrriigghhtt files in
the iiddeeaa directory for conditions of use and distribution
of that component. This software is provided ``as is''
without express or implied warranty.
8 APR 1996 2