NAME

       tcp_table - Postfix client/server table lookup protocol

SYNOPSIS

       postmap -q "string" tcp:host:port

       postmap -q - tcp:host:port <inputfile

DESCRIPTION

       The  Postfix mail system uses optional tables for address rewriting or mail routing. These
       tables are usually in dbm or db format. Alternatively, table lookups can be directed to  a
       TCP server.

       To find out what types of lookup tables your Postfix system supports use the "postconf -m"
       command.

       To test lookup tables, use the "postmap -q" command as described in the SYNOPSIS above.

PROTOCOL DESCRIPTION

       The TCP map class implements a very simple protocol: the client sends a request,  and  the
       server  sends  one  reply.  Requests  and  replies  are  sent  as  one line of ASCII text,
       terminated by the ASCII newline character. Request and reply parameters  (see  below)  are
       separated by whitespace.

       Send and receive operations must complete in 100 seconds.

REQUEST FORMAT

       The  tcp_table  protocol  supports only the lookup request.  The request has the following
       form:

       get SPACE key NEWLINE
              Look up data under the specified key.

       Postfix will not generate partial search keys such as domain names  without  one  or  more
       subdomains,  network  addresses  without  one  or  more least-significant octets, or email
       addresses without the localpart, address extension or domain  portion.  This  behavior  is
       also found with cidr:, pcre:, and regexp: tables.

REPLY FORMAT

       Each  reply  specifies  a  status  code  and  text.  Replies  must  be no longer than 4096
       characters including the newline terminator.

       500 SPACE text NEWLINE
              In case of a lookup request, the requested data does not exist.  The text describes
              the nature of the problem.

       400 SPACE text NEWLINE
              This  indicates  an  error condition. The text describes the nature of the problem.
              The client should retry the request later.

       200 SPACE text NEWLINE
              The request was successful. In the case of a lookup request, the text  contains  an
              encoded version of the requested data.

ENCODING

       In  request  and  reply parameters, the character %, each non-printing character, and each
       whitespace character must be  replaced  by  %XX,  where  XX  is  the  corresponding  ASCII
       hexadecimal  character  value.  The hexadecimal codes can be specified in any case (upper,
       lower, mixed).

       The Postfix client always encodes a request.  The server may omit the encoding as long  as
       the reply is guaranteed to not contain the % or NEWLINE character.

SECURITY

       Do not use TCP lookup tables for security critical purposes.  The client-server connection
       is not protected and the server is not authenticated.

BUGS

       Only the lookup method is currently implemented.

       The client does not hang up when the connection is idle for a long time.

SEE ALSO

       postmap(1), Postfix lookup table manager
       regexp_table(5), format of regular expression tables
       pcre_table(5), format of PCRE tables
       cidr_table(5), format of CIDR tables

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview

LICENSE

       The Secure Mailer license must be distributed with this software.

AUTHOR(S)

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

                                                                                     TCP_TABLE(5)