S/390 PartnerWorld for Developers, ITSO/EFS Project EFS Systems on a Linux Base: Additional Topics

Chapter 3. Networking 29

to connect terminals for systems programmers because this connection requires little or

no customization.

򐂰 SNA 3270 connections. These could be via coax, LANs, or SDLC connections, or through

links to other VTAM or NCP nodes. This was (and still is) a common environment for larger

networks, although many existing installations are moving to TCP/IP bases. There are

many variations of this, with SNA control units and with directly-attached SNA client 3270

emulators.

򐂰 TN3270 TCP/IP connections to z/OS. These are LAN connections using TN3270 clients.

All of these connection modes work with z/OS under FLEX-ES and there are additional

options:

򐂰 Channel-attached S/390 devices

22

(such as 3174s, 3172s, 3745s, and similar control

units) work just as they would on a “real” system. User connections and procedures would

be the same as on a “real” system and we do not further describe this option.

򐂰 Local, non-SNA 3270s can be emulated using the FLEX-ES Terminal Solicitor.

򐂰 LAN SNA and TCP/IP connections can be made through FLEX-ES emulated control units,

and end-user terminals work as they would on a “real” system.

3.2.1 Typical, basic configuration

Most of the FLEX-ES definition examples in this series of redbooks provide a basic network

environment suitable for multiple TSO users and for applications such as CICS, HTTPD, and

WebSphere. The exact purpose and use of the definitions may be a little confusing and this

section describes the usage in more detail.

Our FLEX-ES definition examples include the following lines:

...

cu devad(0x700,3) path(0) resource(CU3174)

cu devad(0xE20,2) path(1) resource(CU3172)

...

...

CU3174: cu 3174 # local, non-SNA 3174 control unit

interface local(1)

device(00) 3278 mstcon # address 700

device(01) 3278 L701 # address 701

device(02) 3278 L702 # address 702

end CU3174

CU3172: cu 3172 # TCP/IP 3172 control unit

interface local(1)

options ‘ipaddress=192.168.0.111,adapternumber=0’

device(00) 3172 eth0 # address E20

device(01) 3172 OFFLINE # address E21

end CU3172

...

Local 3174 connections

The system being emulated is shown in Figure 3-1 on page 30. We can add more terminal

connections to the 3174 by simply adding more lines in the FLEX-ES definitions. We usually

show only three lines to keep the listings shorter. Of course, this assumes that your z/OS has

enough local 3270 devices defined (in its IODF) starting at address 700 to match your

definitions. Our examples assume the z/OS console is defined (in PARMLIB) at address 700

22

At the time of writing, these are not yet available for the Linux version of FLEX-ES. This discussion assumes that

such channels will be available in the future.

30 EFS Systems on a Linux Base: Additional Topics

and that the VTAM definitions have local 3270s defined starting at address 701. (The IODFs

for recent AD CD-ROM systems have 64 local 3270s defined starting at 700. VTAM has 31

terminals defined starting at 701. TSO has only ten VTAM APPLs defined; you can easily add

more.)

Figure 3-1 Emulated configuration

The terminal names shown in the figure (mstcon, L701) are arbitrary names and have no

counterpart on a “real” S/390. On a real S/390, we would connect a coax 3270 terminal to

one of the coax ports on the 3174 control unit. On the FLEX-ES emulation we use a TN3270

session (using x3270, PCOM, or any of a large number of TN3270 products) connected to the

FLEX-ES Terminal Solicitor. The S/390 sees all connections through the Terminal Solicitor as

channel-attached non-SNA 3270 terminals. It does not see that these are actually TN3270

TCP/IP LAN connections.

The Terminal Solicitor accepts TN3270 connections through Linux TCP/IP port 24. If you

point your TN3270 client to the Linux IP address (port 24) and if the FLEX-ES resource

manager is started and if a S/390 instance is started (but not necessarily IPLed), you should

receive the Terminal Solicitor welcome screen. On this screen you can select any of the

named 3270 sessions.

Our examples use a shell script to start two x3270 sessions on the Linux desktop. This can be

viewed as a shortcut through the Terminal Solicitor. With a little more typing, you could

instead manually start two x3270 sessions (on the Linux desktop), connect them to the

Terminal Solicitor, and select the appropriate terminals (which are mstcon and L701 in our

non-SNA 3174 control unit

emulated coax connections

700

701

702

mstcon

L701

L702

3172 TCP/IP control unit

LAN

channel

channel

S/390

E20. E21

Conceptual

System

instance

Resource

Manager

390

FLEX-ES

emulated

3174

emulated

3172

Ter mi nal

Solicitor

mstcon

L701

L702

other Linux

TCP/IP users

desktop

x3270

sessions

Linux

Ethernet adapter eth0

Operational

System

VTAM

TCP/IP

Many users are sharing one physical

Ethernet adapter

192.168.0.111