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TCP_TABLE(5)                                                      TCP_TABLE(5)

<b><a name="name">NAME</a></b>
       tcp_table - Postfix client/server table lookup protocol

<b><a name="synopsis">SYNOPSIS</a></b>
       <b>postmap -q "</b><i>string</i><b>" <a href="tcp_table.5.html">tcp</a>:</b><i>host:port</i>

       <b>postmap -q - <a href="tcp_table.5.html">tcp</a>:</b><i>host:port</i> &lt;<i>inputfile</i>

<b><a name="description">DESCRIPTION</a></b>
       The  Postfix  mail system uses optional tables for address rewriting or
       mail routing. These tables are usually in <b>dbm</b> or  <b>db</b>  format.  Alterna-
       tively, table lookups can be directed to a TCP server.

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

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

<b><a name="protocol_description">PROTOCOL DESCRIPTION</a></b>
       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.

<b><a name="request_format">REQUEST FORMAT</a></b>
       The tcp_table protocol supports only the lookup request.   The  request
       has the following form:

       <b>get</b> SPACE <i>key</i> 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
       <a href="cidr_table.5.html">cidr</a>:, <a href="pcre_table.5.html">pcre</a>:, and <a href="regexp_table.5.html">regexp</a>: tables.

<b><a name="reply_format">REPLY FORMAT</a></b>
       Each  reply specifies a status code and text. Replies must be no longer
       than 4096 characters including the newline terminator.

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

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

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

<b><a name="encoding">ENCODING</a></b>
       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 hexadec-
       imal 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.

<b><a name="security">SECURITY</a></b>
       Do not use TCP lookup  tables  for  security  critical  purposes.   The
       client-server connection is not protected and the server is not authen-
       ticated.

<b><a name="bugs">BUGS</a></b>
       Only the lookup method is currently implemented.

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

<b><a name="see_also">SEE ALSO</a></b>
       <a href="postmap.1.html">postmap(1)</a>, Postfix lookup table manager
       <a href="regexp_table.5.html">regexp_table(5)</a>, format of regular expression tables
       <a href="pcre_table.5.html">pcre_table(5)</a>, format of PCRE tables
       <a href="cidr_table.5.html">cidr_table(5)</a>, format of CIDR tables

<b><a name="readme_files">README FILES</a></b>
       <a href="DATABASE_README.html">DATABASE_README</a>, Postfix lookup table overview

<b><a name="license">LICENSE</a></b>
       The Secure Mailer license must be distributed with this software.

<b>AUTHOR(S)</b>
       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)
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