RFC 1205 (rfc1205) - Page 2 of 12

5250 Telnet interface

RFC 1205                 5250 Telnet Interface             February 1991


   An example of a typical negotiation process to establish 5250 mode of
   operation is shown below.  In this example, the server initiates the
   negotiation by sending the DO TERMINAL-TYPE request.

    Server: IAC DO TERMINAL-TYPE
    Client: IAC WILL TERMINAL-TYPE
    Server: IAC SB TERMINAL-TYPE SEND IAC SE
    Client: IAC SB TERMINAL-TYPE IS IBM-5251-11 IAC SE
    (The client has specified its terminal-type is an IBM-5251-11)

    Server: IAC DO END-OF-RECORD
    Client: IAC WILL END-OF-RECORD
    Server: IAC WILL END-OF-RECORD
    Client: IAC DO END-OF-RECORD
    (The server and client have both agreed to transmit EORs)

    Server: IAC DO TRANSMIT-BINARY
    Client: IAC WILL TRANSMIT-BINARY
    Server: IAC WILL TRANSMIT-BINARY
    Client: IAC DO TRANSMIT-BINARY
    (The server and client have both agreed to binary transmission)

3.  Data Stream Format

   The actual data stream that is exchanged between the client and
   server is composed of a header followed by the 5250 work station data
   stream.  For information about the 5250 work station data stream
   refer to the IBM 5250 Information Display System, Functions Reference
   Manual (SA21-9247).  The header which prefixes the 5250 data stream
   was originally designed for the 5250 Display Station Pass-Through
   (DSPT) application.  5250 DSPT is an application similar to Telnet
   which runs on the IBM AS/400, System/36, and System/38 over an SNA
   network.  This header is designed to be variable in length and is
   composed of two parts.  The first, fixed part is always 6 octets long
   and has the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Logical Record Length     |       Record Type             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |        Reserved               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Logical Record Length:  16 bits

      This field indicates the length, in octets, of this logical record
      including the header length.  The length is calculated BEFORE



Chmielewski