I can't tell you any more that the docs for nsca do. But I'll see if any of this helps.
On the remote host is the send_nsca.cfg file. It should be setup correctly with the same encoding as the daemon config file.
On the remote host, you should have a checkcommands.cfg with:
command_line $USER1$/eventhandlers/submit_check_result $HOSTNAME$ '$SERVICEDESC$' $SERVICESTATE$ '$OUTPUT$|$PERFDATA$'
On the remote host, you should have a file in
$USER1$/eventhandlers named submit_check_result.
That file should be like this:
# $1 = host_name (Short name of host that the service is
# associated with)
# $2 = svc_description (Description of the service)
# $3 = state_string (A string representing the status of
# the given service - "OK", "WARNING", "CRITICAL"
# or "UNKNOWN")
# $4 = plugin_output (A text string that should be used
# as the plugin output for the service checks)
# Convert the state string to the corresponding return code
case "$3" in
# pipe the service check info into the send_nsca program, which
# in turn transmits the data to the nsca daemon on the central
# monitoring server
/bin/echo "$1\\t$2\\t$return_code\\t$4\\n" | /export/home/nagios/bin/send_nsca ipofnagiosserver -c /export/home/nagios/etc/send_nsca.cfg
You should be able to use the contents of this file as a guide on how to sent the file from a unix prompt on the remote host.
The contents of that test would have to have a real hostname as defined on the nagios server plus a valid service description, a valid return code, and then finally some fake plugin output.
If you can't succesfully run the command, then check your configs again.