Networking on z/OS
Previous topic | Next topic | Contents | Glossary | Contact z/OS | PDF


Examples of controlling TCP/IP applications

Networking on z/OS

There are individual commands to control the more significant (that is, well known and well used) TCP/IP applications. There are MODIFY commands to control the IKE server, OMPROUTE, the policy agent SNMP and others. In this section, the FTP server and TN3270E server are discussed.

FTP server

The FTP server supports the ability dynamically to activate and to deactivate several different debugging options through the MODIFY command.
MODIFY ftpdjobname,DEBUG=(parm)
The DEBUG parameter can take several different operands such as:
CMD
Trace of FTP subcommand activity
SEC
Trace of FTP security (TLS) functions
SOC
Trace of FTP socket activity
NONE
Turn off FTP server tracing
There are other operands available, as well as the ability to trace a specific user ID. For example, the command to activate tracing of FTP subcommand and security processing for the user ID MATT is:
F FTPD1,DEBUG=(CMD,SEC,USERID(MATT))

Interpretation of an FTP trace requires in-depth knowledge of both z/OS and FTP. Often, FTP traces are taken at the advice of IBM service personnel, who also handle the interpretation of the output.

TN3270E server

The command suite for controlling the TN3270E server is large for two reasons. First, the TN3270E server is the foremost method of communicating with the mainframe. Second, the TN3270E server straddles SNA and IP, which means it must operate with consideration for both environments.

Examples of displaying the TN3270E server

The DISPLAY TCPIP,telenetprocname,TELNET command supports a large suite of operands that affords the network administrator either a wide or narrow view of the TN3270E server. Operands can produce summaries or detailed displays about individual aspects of the server.

For example, if a network administrator wanted a complete view of the configuration of an active TN3270E server, the following command could be used:
D TCPIP,TELNETS,TELNET,PROFILE,DETAIL
The resulting output from this command has been edited for brevity and can be seen in Figure 1. Of interest are such fields as the following:
PERSISTANCE
This section includes the LUSESSIONPEND parameter, which controls whether the user is returned to a logon-type panel after logging off of an application.
DIAGNOSTICS
This section shows what tracing is active.
SECURITY
This section shows the type of connections allowed. A BASIC connection contains no TLS security.
TIMERS
The inactivity timers are important to the TN3270E server in event of network outages or clients that fail to indicate the connection has ended.

The total number of records displayed is indicated at the bottom of this display command. This simple command resulted in 85 records. This command provides considerably more detail about the active TN3270E server's profile than what has been shown.

Figure 1. DISPLAY TELNET PROFILE command (edited)
 EZZ6080I TELNET PROFILE DISPLAY 
 ....
 PERSISTENCE                                                
   NOLUSESSIONPEND                                          
   NOMSG07                                                  
   NO TKOSPECLU 
   NO TKOGENLU                                            
   NO QUEUESESSION                                        
   NODROPASSOCPRINTER                                     
   KEEPLU                  0 (OFF)                        
   ....
 DIAGNOSTICS                                              
   DEBUG             EXCEPTION                            
   DEBUG ROUTING     CONSOLE                              
   NOFULLDATATRACE                                        
 SECURITY                                                 
   PORT                   23                              
   CONNTYPE          BASIC                                
   KEYRING           **N/A** 
 ....
 TIMERS                           
   INACTIVE                0 (OFF)
   KEEPINACTIVE            0 (OFF)
   PRTINACTIVE             0 (OFF)
The other commonly use DISPLAY command is the following:
D TCPIP,telnetprocname,TELNET,CONN

Figure 2 shows the output from this command. Using this command is a quick way for a network administrator to determine all active connections to the TN3270E server. It is similar to the DISPLAY NETSTAT command with a filter on port 23, except that basic TN3270E information is included.

The field TSP PTR stands for terminal, session, protocol pointer. The terminal column describes whether the connect is for a terminal (T) or printer (P) (all connections are for terminals, in this example).

The session column indicates whether the session is active (A), pending (P), or negotiating (N) (not shown in this example). The last column, protocol, is normally for TN3270E, but sometimes a 3 could show up here, indicating a TN3270 connection is in use (there are other possible protocols, but they are extremely rare).

Figure 2. DISPLAY TELNET CONNECTION command
 EZZ6064I TELNET CONNECTION DISPLAY 
         EN                                            TSP         
 CONN     TY IPADDR..PORT            LUNAME   APPLID   PTR LOGMODE 
 -------- -- ---------------------- -------- --------  --- --------
 000188B7    192.168.105.20..1568   OVHTCP27 OVHSAMON  TAE SNX32705
 000171B3    192.168.185.29..3554   OVHTCP21 OVHTSO17  TAE SNX32702
 00015AF1    192.168.185.90..3183   OVHTCP14 OVHTSO27  TPE SNX32705
 000157CA    192.168.185.79..3008   OVHTCP12 OVHTSO38  TAE SNX32702
 ----- PORT:    23  ACTIVE               PROF: CURR CONNS:      4  
 ------------------------------------------------------------      
 6 OF 6 RECORDS DISPLAYED 

Control of the TN3270E server

The TN3270E server also supports extensive control commands:
VARY TCPIP,telnetprocname,ACT,luname
Commands for activating and inactivating LUs are available. However, they are not the same as a VTAM activation of a resource. A command to inactivate a TN3270 LU simply makes an LU unavailable to the TN3270E server; it has no effect on the resource status. Such a command might be used by the network administrator in the event of an LU causing connectivity problems. To inactivate LU OVHTCP12, the following command could be used:
V TCPIP,telnetprocname,INACT,OVHTCP12

At startup of the TN3270E server, all LUs are considered active (available) by default.

There are also commands to stop and restart TN3270E services without having to actually stop or restart the TN3270E server.

Go to the previous page   |   Go to the next page




Copyright IBM Corporation 1990, 2010