SFECHO
Section: User Commands (1)
Updated: 8 APR 1996
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NAME
sfecho - Speak Freely remote echo server
SYNOPSIS
sfecho
[
-du
]
[
-pport
]
[
-vtimeout
]
DESCRIPTION
sfecho
is a server program which receives sound from remote hosts in
the same manner as
sfspeaker,
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
different compression and encryption modes to optimise
end-to-end performance without tying up a person on the
other end of the connection.
sfecho
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
sfspeaker
manual page for details on how to set the environment variables.
OPTIONS
- -d
-
Enables debug output from
sfecho.
- -pport
-
Causes
sfecho
to listen on the specified port number instead of the default
port specified by ``INTERNET_PORT'' in the
Makefile.
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.
- -u
-
Prints how-to-call information.
- -vtimeout
-
When
sfecho
receives a packet from a host it hasn't heard from in
timeout
seconds, it will attempt to find the host name and print a
message on standard error noting the new connection and what
compression mode is being used. If the
host name can't be found, the numeric IP address is given.
After
timeout
seconds of inactivity a message is issued indicating the host is idle.
If no
timeout
is specified, 180 seconds is used.
BUGS
If
sfecho
runs out of memory to buffer sound awaiting retransmission,
packets are discarded without warning.
By default,
sfecho
listens on Internet port number 2074, the same as
sfspeaker,
and hence cannot run at the same time on the same machine as
sfspeaker.
You can specify a different port for
sfecho
with the
-p
option, but many users have difficulty connecting to servers with
nonstandard 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.
ACKNOWLEDGEMENTS
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.
SEE ALSO
sfspeaker(1)
AUTHOR
-
John Walker
WWW: http://www.fourmilab.ch/
All modules of
Speak Freely
developed by me are in the public domain.
See the
readme
and/or
copyright
files in the
idea
directory for conditions of use and distribution of that
component. This software is provided ``as is'' without express or
implied warranty.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- BUGS
-
- ACKNOWLEDGEMENTS
-
- SEE ALSO
-
- AUTHOR
-
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Time: 12:37:46 GMT, July 10, 2022