IBM i Series, Handbook

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TCP/IP Connectivity Utilities (5722-TC1)
563
TCP/IP Connectivity Utilities (5722-TC1)
Telnet client and server
The Telnet protocol allows a system (the Telnet client) to access and use the resources of a
remote system (the Telnet server) as if the Telnet client's workstation were locally connected
to the remote system. iSeries Telnet provides both the Telnet client and the Telnet server
functions. The Telnet protocol provides a mechanism for the client and server to negotiate
options that control the operating characteristics of a Telnet connection. Among other things,
these negotiations involve determining the best terminal type supported by both the client
and server.
Depending on the terminal type negotiated, the iSeries Telnet client operates in one of the
following full-screen modes: 3270, 5250, VT100 or VT220. The iSeries Telnet server operates
in ASCII line mode or in one of the following full-screen modes: 3270, 5250 or VT100. The
functions available in a Telnet session depend on the operating mode. Security and
automation features are included in the iSeries Telnet 5250 server:
Registered Telnet server exits for both session initialization and session termination. These
exits require only that a customer-written user exit program be registered at the proper exit
point. No changes are needed for the connecting Telnet client emulator, so existing clients
can immediately benefit from this feature.
Virtual Device selection by the attaching client (or a registered Telnet server exit program)
provides for more traditional job-routing to preferred subsystems and allows for associated
work management tuning. With Virtual Device selection, preferred code page, character set,
and keyboard attributes can be established on a per session basis, thereby offering greater
flexibility in national language support.
Printer Passthru support consists of two new terminal (IBM 3812-1 and IBM 5553-B01) which
provide additional printer support for the TCP/IP environment. This support allows the Telnet
server to provide the client with the flexibility to dynamically create and/or select a virtual
printer device through enhanced negotiation, or via assignment by the initialization exit
program.
Telnet server supports secure Telnet sessions via SSL.
Network Address Translation (NAT) TCP/IP Address Mapping and Hiding
When the TCP/IP addressing schemes of networks conflict, or you need to hide all or part of
the network topology, network address translation (NAT) capabilities provide a solution. In
addition, TCP/IP address hiding allows all the computers on one network to access servers
on another network by sharing a single TCP/IP address. Masquerading is particularly useful
when connecting to another network, such as the Internet, using a dial-up link.