TCP_TABLE(5)                                                      TCP_TABLE(5)

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)