[Joerg Mayer <jmayer@xxxxxxxxx>]

As a small exercise, I've tried to write a dissector for the rdate
protocol - and failed:
When I start tethereal, it dies with the following message:

** ERROR **: file proto.c: line 2227 (proto_register_protocol): assertion failed: (g_list_find_custom(protocols, name, proto_match_name) == NULL)
aborting...

I've attached packet-rdate.c. There is one other thing to look at:
A time request is just a udp packet to port 37 without any payload.
Is the code I wrote valid for that case?

 Thanks
   Jï¿œrg
-- 
Joerg Mayer                                           <jmayer@xxxxxxxxx>
We are stuck with technology when what we really want is just stuff that
works. Some say that should read Microsoft instead of technology.

/* packet-rdate.c
 * Routines for Time Protocol dissection
 * Copyright 2004, Joerg Mayer (email see AUTHORS file)
 *
 * $Id: README.developer,v 1.90 2004/02/14 10:37:22 obiot Exp $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@xxxxxxxxxxxx>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <glib.h>
#include <epan/packet.h>

#define RDATE_PORT 37

/* Initialize the protocol and registered fields */
static int proto_rdate = -1;
static int hf_rdate_seconds = -1;

/* Initialize the subtree pointers */
static gint ett_rdate = -1;

/* Code to actually dissect the packets */
static void
dissect_rdate(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{

	proto_item	*ti;
	proto_tree	*rdate_tree;

	char		*datestring = "Todo";
	guint32		seconds;
	guint32		length = 0;

	if (check_col(pinfo->cinfo, COL_PROTOCOL)) 
		col_set_str(pinfo->cinfo, COL_PROTOCOL, "rdate");
    
	if (check_col(pinfo->cinfo, COL_INFO)) 
		col_clear(pinfo->cinfo, COL_INFO);

	if (tree) {

	        length = tvb_length_remaining (tvb, 0);

		if (length) {
			seconds = tvb_get_ntohl(tvb, 0);
			if (check_col(pinfo->cinfo, COL_INFO)) 
				col_add_fstr(pinfo->cinfo, COL_INFO, "Reply: %u secs (%s)", seconds, datestring);

			ti = proto_tree_add_item(tree, proto_rdate, tvb, 0, 4, FALSE);

			rdate_tree = proto_item_add_subtree(ti, ett_rdate);
			proto_tree_add_protocol_format(rdate_tree,
				hf_rdate_seconds, tvb, 0, length, "Rdate Reply: %u secs (%s)", seconds, datestring);
		} else {
			if (check_col(pinfo->cinfo, COL_INFO)) 
				col_set_str(pinfo->cinfo, COL_INFO, "Request");
			proto_tree_add_protocol_format(rdate_tree,
				hf_rdate_seconds, tvb, 0, 0, "Rdate Request");
		}
	}
}

void
proto_register_rdate(void)
{                 

	static hf_register_info hf[] = {
		{ &hf_rdate_seconds,
			{ "Seconds",           "rdate.seconds",
			FT_UINT32, BASE_DEC, NULL, 0x0,          
			"Seconds since 1.1.1900 0:00",
			HFILL }
		},
	};

	static gint *ett[] = {
		&ett_rdate
	};

	proto_rdate = proto_register_protocol("Time Protocol",
	    "RDATE", "rdate");
	proto_register_field_array(proto_rdate, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
}


void
proto_reg_handoff_rdate(void)
{
	dissector_handle_t rdate_handle;

	rdate_handle = create_dissector_handle(dissect_rdate,
	    proto_rdate);
	dissector_add("tcp.port", RDATE_PORT, rdate_handle);
	dissector_add("udp.port", RDATE_PORT, rdate_handle);
}