MCHAT(1) BSD Reference Manual MCHAT(1)NAMEmchat - tiny multicast chat client
SYNOPSISmchat [-dD] [-i interface] [-l hoplimit] [-P policy] address port
DESCRIPTION
The mchat is a tiny multicast chat program. mchat uses single multicast
group, specified in address, as communication channel among clients. No
server is necessary. If you would like to communicate with remote end,
you need to have multicast reachability between your location and other
participants.
Lines starting with ``/'' will be recognized as commands. The following
commands are recognized:
/who Query members on the chat channel. Since the command relies upon
replies from peers, there can be ``hidden'' listeners on the
channel. /w can be used as well.
/secret address message
Send secret message to address by unicast channel. The traffic
will be sent by unicast, and will not be visible to other people.
/s can be used as well.
/name [name]
Configure your name for the chat channel. If name is omitted, it
will be re-initialized to the result of getlogin(2).
/file file
Send data of file.
/log [file]
Save received data into file. If /log is typed again, logging
will be finished.
/help Shows command help (/h for short).
/quit Terminate mchat (/q for short).
If you type any string (that does not start with ``/''), that will be
sent to multicast address address, UDP port port with minimal encoding.
String typed by peers will be shown onto your tty.
mchat is able to transmit secret message to only one of the participants,
by using ``secret'' command, described above. secret command uses UDP
port next to port (port + 1). Secret message can be encrypted by using
IPsec, if you configure IPsec and/or key exchange program properly.
The following command line options are recognized:
-d Turns on debugging mode (currently has no effect).
-Dmchat usually uses curses(3) for rendering screen, where possi-
ble. -D forces mchat to use dumb terminal mode (no curses).
-i interface
Specifies outgoing network interface for multicast packets.
-l hoplimit
Specifies hoplimit (or time-to-live for IPv4) for multicast pack-
ets.
-P policy
Specifies IPsec policy string to be used for unicast packets.
Refer to ipsec_set_policy(3) on how to specify policy string.
EXAMPLES
Lines starting with ``>>'' are messages from mchat program itself.
% mchat-i ne2 ff02::1 8999
>> itojun joined
/w
>> itojun@lychee.itojun.org (3ffe:501:808:fff0:200:86ff:fe05:80fa)
>> masa@anago.fumi.net (3ffe:501:808:fff0:200:86ff:fe31:c5c7)
hi
[itojun] hi
[masa] hi welcome back!
/s 3ffe:501:808:fff0:200:86ff:fe31:c5c7 this is a secret message
>> making secret message to 3ffe:501:808:fff0:200:86ff:fe31:c5c7
RETURN VALUESmchat will exit with positive value on errors.
HISTORY
The mchat command first appeared in WIDE/KAME IPv6 protocol stack kit.
BUGS
IPv4 is not supported at this moment.
Multicast group and UDP port number should officially be allocated.
Security consideration: multicast channel is subject to wiretap, as there
is no encryption provided for the channel. Unicast channel can be en-
crypted for secrecy but it needs proper configuration of IPsec.
Multilingual encodings needs to be supported.
KAME Autumn 3, 1999 2
