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For additional information about sockets, refer to the
Sockets Programming
,
SC41-5422-03 book.
Using X.25 PVC instead of SVC
In “Step 5—Configuring TCP/IP Remote System Information (X.25)” on page 36 you
were shown how to define the X.25 network address of each system that uses a
switched virtual circuit (SVC).
To replace the X.25 SVC with an X.25 permanent virtual circuit (PVC) connection,
the example below is helpful. The following CL commands will look different:
CRTLINX25, ADDTCPIFC, and ADDTCPRSI.
Use the same X.25 line description, but replace the first of the four SVCs with a
PVC.
CRTLINX25 LIND(X25LINE) RSRCNAME(LIN051)
LGLCHLE((001 *PVC) (002 *SVCBOTH)
(003 *SVCBOTH) (004 *SVCBOTH))
NETADR(40030003) CNNINIT(*LOCAL)
TEXT('ITSO X.25 Network')
The TCP/IP interface now points to a specific PVC instead of a pool of SVCs.
ADDTCPIFC INTNETADR('9.4.73.65') LIND(X25LINE)
SUBNETMASK('255.255.255.192') PVCLGLCHLI(001)
MAXSVC(0)
The TCP/IP remote system information no longer includes the X.25 address to be
called. Instead, the entry points to the PVC channel ID.
ADDTCPRSI INTNETADR('9.4.73.66')
PVCLGLCHLI(001)
IP Multicasting
IP multicasting is the process of transmitting an IP datagram to a host group. The
hosts that are in the group may reside on a single subnet or on different subnets
that are connected by multicast-capable routers. Hosts may join and leave groups
at any time. There are no restrictions on the location or number of members in a
host group. For more information about IP multicasting, refer to RFC 1112,
Host
Extensions for IP Multicasting
.
Note: The AS/400 cannot act as a multicast-capable router.
Multicast Application Programming Information
An application program can send or receive multicast datagrams by using the
Sockets API and connectionless, SOCK_DGRAM type sockets. Multicasting is a
one-to-many transmission method. You cannot use connection-oriented sockets of
type SOCK_STREAM for multicasting. When a socket of type SOCK_DGRAM is
created, an application can use the setsockopt() function to control the multicast
characteristics associated with that socket. The setsockopt() function accepts the
following IPPROTO_IP level flags:
v IP_ADD_MEMBERSHIP: Joins the multicast group specified.
Chapter 3. TCP/IP: Operation, Management, and Advanced Topics 91