epmd

Richard Barrett <>
Fri May 26 15:23:52 CEST 2000


I am a newcomer to erlang and in my spare time trying to learn about 
it. I've got a problem with the the process monitor daemon, epmd, 
which may be due to my ignorance. It goes as follows:

Whenever I start an erlang process using erl -name ..., another copy 
of epmd is also created. This is regardless of whether an instance of 
epmd is already running as a a result of my having run it explicitly 
from the command line or previously started another instance of erl. 
I've checked using netstat and lsof and all these instances of epmd 
are trying to listen on port 4369.

Having started multiple instances of erl from different terminal 
windows, it appears that only the epmd process started by the most 
recently executed erl command will respond to an epmd -names command 
and it only reports knowing the name of the erl process that invoked 
it. Killing the most recent epmd will "expose" the "prior" invocation 
of epmd which still only reports the name of the erl process that ran 
it, and is equally ignorant of the names any other erl processes that 
are running.

Closing down an erl process does not lead to the corresponding epmd 
process terminating. Over a period of time this leaves growing 
numbers of epmd process in the system. It also leads to confusion in 
inter-erl-process communications and asymmetry in what inter-process 
communication can be performed.

This arrangement is not what I'd expected. I had assumed that once 
there was an instance of epmd in the system subsequent invocations of 
erl would communicate with that epmd process rather than invoking 
another. I'd also assumed the single epmd would report all of the 
named erl process in the system.

Can anyone tell me what I'm doing wrong or suggest where I might look 
in the documentation or source for a solution to this.

I am running erlang installed from erlang_otp-R6B-4.i386.rpm under 
Suse 6.2 Linux.

Thanks, in advance, for your help.

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Benjamin Franklin, 1759
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