Using Port Monitors

RPC servers can be started by port monitors such as inetd and listen. Port monitors listen for requests and spawn servers in response. The forked server process is passed file descriptor 0 on which the request has been accepted. For inetd, when the server is done, it may exit immediately or wait a given interval for another service request.

For listen, servers should exit immediately after replying because listen() always spawns a new process. The following function call creates a SVCXPRT handle to be used by the services started by port monitors:

transp = svc_tli_create(0, nconf, (struct t_bind *)NULL, 0, 0)

nconf is the netconfig structure of the transport from which the request is received.

Because the port monitors have already registered the service with rpcbind, there is no need for the service to register with rpcbind. But it must call svc_reg() to register the service procedure:

svc_reg(transp, PROGNUM, VERSNUM, dispatch,(struct netconfig *)NULL)

The netconfig structure here is NULL to prevent svc_reg() from registering the service with rpcbind.

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Note -

Study rpcgen-generated server stubs to see the sequence in which these routines are called.

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For connection-oriented transports, the following routine provides a lower level interface:

transp = svc_fd_create(0, recvsize, sendsize);

A 0 file descriptor is the first argument. You can set the value of recvsize and sendsize to any appropriate buffer size. A 0 for either argument causes a system default size to be chosen. Application servers that do not do any listening of their own use svc_fd_create().

Using inetd

Entries in /etc/inet/inetd.conf have different formats for socket-based, TLI-based, and RPC services. The format of inetd.conf entries for RPC services is:

rpc_prog/vers endpoint_type rpc/proto flags user pathname args
where: 

Table 4-9 RPC inetd Services

rpc_prog/vers	The name of an RPC program followed by a / and the version number or a range of version numbers.
endpoint_type	One of dgram (for connectionless sockets), stream (for connection mode sockets), or tli (for TLI endpoints).
proto	May be * (for all supported transports), a nettype, a netid, or a comma separated list of nettype and netid.
flags	Either wait or nowait.
user	Must exist in the effective passwd database.
athname	Full path name of the server daemon.
args	Arguments to be passed to the daemon on invocation.

For example:

rquotad/1 tli rpc/udp wait root /usr/lib/nfs/rquotad rquotad

For more information, see the inetd.conf(4) man page.

Using the Listener

Use pmadm to add RPC services:

pmadm -a -p pm_tag -s svctag -i id -v vers \

 	-m `nlsadmin -c command -D -R prog:vers`

The arguments are: -a means to add a service, -p pm_tag specifies a tag associated with the port monitor providing access to the service, -s svctag is the server's identifying code, -i id is the /etc/passwd user name assigned to service svctag, -v ver is the version number for the port monitor's data base file, and -m specifies the nlsadmin command to invoke the service. nlsadmin can have additional arguments. For example, to add version 1 of a remote program server named rusersd, a pmadm command is:

# pmadm -a -p tcp -s rusers -i root -v 4 \
   -m `nlsadmin -c /usr/sbin/rpc.ruserd -D -R 100002:1`

The command is given root permissions, installed in version 4 of the listener data base file, and is made available over TCP transports. Because of the complexity of the arguments and options to pmadm, use a command script or the menu system to add RPC services. To use the menu system, enter sysadm ports and choose the -port_services option.

After adding a service, the listener must be re-initialized before the service is available. To do this, stop and restart the listener, as follows (note that rpcbind must be running):

# sacadm -k -p pmtag
# sacadm -s -p pmtag

For more information, such as how to set up the listener process, see the listen(1M), pmadm(1M), sacadm(1M) and sysadm(1M) man pages and the TCP/IP and Data Communications Administration Guide.