clnt_broadcast - Linux

Overview

The clnt_broadcast command broadcasts a Remote Procedure Call (RPC) message to a set of network nodes. It is a vital tool for distributed computing systems, allowing clients to communicate asynchronously with multiple servers.

Syntax

clnt_broadcast UDPPROGPROGNUM UDSOCKETPATH GROUP-ADDRESS

Parameters

  • UDPPROGPROGNUM: The UDP port number of the RPC program specified as a hexadecimal value.
  • UDSOCKETPATH: The UNIX domain socket path of the RPC program.
  • GROUP-ADDRESS: The multicast address to which the RPC message is broadcast.

Options/Flags

clnt_broadcast has no additional options or flags.

Examples

Example 1: Broadcasting a Simple Message

clnt_broadcast 8E4E 0 /etc/rpc/mountd.sock 224.0.0.25

This command broadcasts an RPC message with the program number 8E4E to all nodes that have subscribed to the multicast address 224.0.0.25. The UNIX domain socket path is /etc/rpc/mountd.sock.

Example 2: Broadcasting a Complex Message

clnt_broadcast 8C06 /nfs/rpc \
    /var/nfs/rpc/mountd.sock \
    224.0.0.25 mnt_exports /dev/sda1

This command broadcasts a more complex RPC message with the program number 8C06. It exports the file system /dev/sda1 using the mount point /mnt/exports. The additional arguments are specific to the NFS protocol.

Common Issues

Error: No hosts responded to the broadcast.

This error can occur if no nodes are listening on the specified multicast address. Ensure that the correct multicast address is used and that firewall settings allow communication on that address.

Error: Invalid UDP port number.

The UDP port number must be a hexadecimal value between 0x0000 and 0xFFFF. Verify that the specified port number is correct.

Integration

clnt_broadcast can be integrated into scripts to automate RPC broadcasts. For example:

#!/bin/bash
# Broadcast a message to mount the NFS share on all nodes
clnt_broadcast 8C06 /nfs/rpc \
    /var/nfs/rpc/mountd.sock \
    224.0.0.25 mnt_exports /dev/sda1

Related Commands

  • rpcgen: Generates RPC program stub files.
  • rpcinfo: Provides information about RPC programs and services.
  • rpcd: The RPC daemon that manages RPC requests.