2.11BSD#431 - /usr/man/cat8/popper.0

popper(8)	    UNIX Programmer's Manual		popper(8)


NAME
     popper - pop 3 server

SYNOPSIS
     /usr/libexec/popper [ -d ] [ -t trace-file]

DESCRIPTION
     Popper is an implementation  of  the  Post  Office  Protocol
     server  that  runs  on a variety of Unix computers to manage
     electronic mail for Macintosh  and  MS-DOS  computers.   The
     server  was  developed  at  the  University of California at
     Berkeley and conforms fully to  the  specifications  in  RFC
     1081  and RFC 1082.  The Berkeley server also has extensions
     to send electronic mail on behalf of a client.

     The -d flag sets the socket to debugging and turns on debug-
     ging.   All  debugging information is saved using syslog(8).
     The -t trace-file flag turns  on  debugging  and  saves  the
     trace information in trace-file using fprintf(s).

HOW TO OBTAIN THE SERVER
     The  POP  server  is  available  via  anonymous   ftp   from
     ftp.CC.Berkeley.EDU (128.32.136.9, 128.32.206.12).  It is in
     two files in  the	pub  directory:  a  compressed	tar  file
     popper.tar.Z  and a Macintosh StuffIt archive in BinHex for-
     mat called MacPOP.sit.hqx.

THE POP TRANSACTION CYCLE
     The Berkeley POP server is a single program (called  popper)
     that  is launched by inetd when it gets a service request on
     the POP TCP port.	(The official port  number  specified  in
     RFC  1081 for POP version 3 is port 110.  However, some POP3
     clients attempt to contact the server at port 109,  the  POP
     version  2  port.	Unless you are running both POP2 and POP3
     servers, you can simply define both ports	for  use  by  the
     POP3 server.  This is explained in the installation instruc-
     tions later on.) The popper program initializes and verifies
     that  the peer IP address is registered in the local domain,
     logging a warning message when a connection  is  made  to	a
     client whose IP address does not have a canonical name.  For
     systems using BSD 4.3 bind, it also checks to see if a  can-
     nonical  name lookup for the client returns the same peer IP
     address, logging a warning message if it does not.  The  the
     server  enters  the  authorization  state,  during which the
     client must correctly identify itself by providing  a  valid
     Unix  userid  and password on the server's host machine.  No
     other exchanges are allowed during this state (other than	a
     request  to  quit.)  If authentication fails, a warning mes-
     sage is logged and the session ends.  Once the user is iden-
     tified,  popper changes its user and group ids to match that
     of the user and enters the transaction  state.   The  server
     makes a temporary copy of the user's maildrop (ordinarily in


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popper(8)	    UNIX Programmer's Manual		popper(8)


     /usr/spool/mail) which is used for all  subsequent  transac-
     tions.   These  include the bulk of POP commands to retrieve
     mail, delete mail, undelete mail, and so forth.  A  Berkeley
     extension	also  allows  the user to submit a mail parcel to
     the server who mails it using  the  sendmail  program  (this
     extension	is  supported in the HyperMail client distributed
     with the server).	When the client quits, the server  enters
     the  final  update state during which the network connection
     is terminated and the user's maildrop is  updated	with  the
     (possibly) modified temporary maildrop.

LOGGING
     The POP server uses syslog to keep a record of  its  activi-
     ties.   On  systems with BSD 4.3 syslogging, the server logs
     (by default) to the "local0" facility at  priority  "notice"
     for  all messages except debugging which is logged at prior-
     ity    "debug".	  The	  default     log     file     is
     /usr/spool/mqueue/POPlog.	These can be changed, if desired.
     On systems with 4.2 syslogging all messages  are  logged  to
     the local log file, usually /usr/spool/mqueue/syslog.

DEBUGGING
     The popper program will log debugging information	when  the
     -d  parameter  is	specified  after  its  invocation  in the
     inetd.conf file.  Care should be  exercised  in  using  this
     option  since it generates considerable output in the syslog
     file.  Alternatively, the "-t <file-name>" option will place
     debugging	information into file "<file-name>" using fprintf
     instead of syslog.

     For SunOS version 3.5, the popper	program  is  launched  by
     inetd  from  /etc/servers.   This file does not allow you to
     specify command line arguments.  Therefore, if you  want  to
     enable   debugging,  you  can  specify  a	shell  script  in
     /etc/servers to be launched instead of popper  and  in  this
     script call popper with the desired arguments.

     You can confirm that the POP server is running  on  Unix  by
     telneting	to  port  110 (or 109 if you set it up that way).
     For example:

     %telnet myhost 110
     Trying...
     Connected to myhost.berkeley.edu.
     Escape character is '^]'.
     +OK UCB Pop server (version 1.6) at myhost starting.
     quit
     Connection closed by foreign host.

VERSION 1.7 RELEASE NOTES
     Extensive re-write of the maildrop processing  code  contri-
     buted  by	Viktor	Dukhovni <viktor@math.princeton.edu> that


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     greatly reduces the possibility that  the	maildrop  can  be
     corrupted	as  the  result  of simultaneous access by two or
     more processes.

     Added "pop_dropcopy" module to create a  temporary  maildrop
     from  the	existing,  standard  maildrop  as root before the
     setuid and setgid for the user is	done.	This  allows  the
     temporary	maildrop  to be created in a mail spool area that
     is not world read-writable.

     This version does *not* send the sendmail "From "	delimiter
     line in response to a TOP or RETR command.

     Encased all debugging code in #ifdef DEBUG constructs.  This
     code  can be included by specifying the DEGUG compiler flag.
     Note:  You still need to use the -d or -t option  to  obtain
     debugging output.

LIMITATIONS
     The POP server copies the user's entire maildrop to /tmp and
     then operates on that copy.  If the maildrop is particularly
     large, or inadequate space is available in  /tmp,	then  the
     server will refuse to continue and terminate the connection.

     Simultaneous modification of a single maildrop can result in
     confusing	results.  For example, manipulating messages in a
     maildrop using the Unix /usr/ucb/mail command while  a  copy
     of  it  is  being	processed by the POP server can cause the
     changes made by one program to be lost when the  other  ter-
     minates.	This problem is being worked on and will be fixed
     in a later release.

FILES
     /usr/spool/mail	     mail files
     /etc/inetd.conf	     pop program invocation
     /etc/syslog.conf	     logging specifications

SEE ALSO
     inetd(8), RFC1081, RFC1082

AUTHORS
     Bob Campbell, Edward Moy, Austin Shelton, Marshall  T  Rose,
     and cast of thousands at Rand, UDel, UCI, and elsewhere


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