RFC 1205 (rfc1205) - Page 2 of 12
5250 Telnet interface
Alternative Format: Original Text Document
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