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

       Each request specifies a command, a lookup key, and possibly a lookup result.

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

       put SPACE key SPACE value NEWLINE
              This request is currently not implemented.

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.   In  case  of  an
              update  request,  the  request  was rejected.  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

                                                                                     TCP_TABLE(5)