/// <summary>
        /// Adds the given remote device to the network.
        /// </summary>
        /// <remarks>Notice that this operation does not join the remote XBee device to the network; it
        /// just tells the network that it contains that device. However, the device has only been added
        /// to the device list, and may not be physically in the same network.
        ///
        /// The way of adding a device to the network is based on the 64-bit address. If it is not
        /// configured:
        /// <list type="bullet">
        /// <item><description>For 802.15.4 and ZigBee devices, it will use the 16-bit address.</description></item>
        /// <item><description>For the rest will return <c>true</c> as the result of the addition.</description></item>
        /// </list></remarks>
        /// <param name="remoteDevice">The remote device to be added to the network.</param>
        /// <returns>The remote XBee Device instance in the network, <c>null</c> if the device could not be
        /// successfully added.</returns>
        /// <exception cref="ArgumentNullException">If <c><paramref name="remoteDevice"/> == null</c>.</exception>
        public RemoteXBeeDevice AddRemoteDevice(RemoteXBeeDevice remoteDevice)
        {
            if (remoteDevice == null)
            {
                throw new ArgumentNullException("Remote device cannot be null.");
            }

            logger.DebugFormat("{0}Adding device '{1}' to network.", localDevice.ToString(), remoteDevice.ToString());

            RemoteXBeeDevice devInNetwork = null;
            XBee64BitAddress addr64       = remoteDevice.XBee64BitAddr;
            XBee16BitAddress addr16       = Get16BitAddress(remoteDevice);

            // Check if the device has 64-bit address.
            if (addr64 != null && !addr64.Equals(XBee64BitAddress.UNKNOWN_ADDRESS))
            {
                // The device has 64-bit address, so look in the 64-bit map.
                if (remotesBy64BitAddr.TryGetValue(addr64, out devInNetwork))
                {
                    // The device exists in the 64-bit map, so update the reference and return it.
                    logger.DebugFormat("{0}Existing device '{1}' in network.", localDevice.ToString(), devInNetwork.ToString());
                    devInNetwork.UpdateDeviceDataFrom(remoteDevice);
                    return(devInNetwork);
                }
                else
                {
                    // The device does not exist in the 64-bit map, so check its 16-bit address.
                    if (addr16 != null && !addr16.Equals(XBee16BitAddress.UNKNOWN_ADDRESS))
                    {
                        // The device has 16-bit address, so look in the 16-bit map.
                        if (remotesBy16BitAddr.TryGetValue(addr16, out devInNetwork))
                        {
                            // The device exists in the 16-bit map, so remove it and add it to the 64-bit map.
                            logger.DebugFormat("{0}Existing device '{1}' in network.", localDevice.ToString(), devInNetwork.ToString());
                            remotesBy16BitAddr.TryRemove(addr16, out devInNetwork);
                            devInNetwork.UpdateDeviceDataFrom(remoteDevice);
                            remotesBy64BitAddr.AddOrUpdate(addr64, devInNetwork, (k, v) => devInNetwork);
                            return(devInNetwork);
                        }
                        else
                        {
                            // The device does not exist in the 16-bit map, so add it to the 64-bit map.
                            remotesBy64BitAddr.AddOrUpdate(addr64, remoteDevice, (k, v) => remoteDevice);
                            return(remoteDevice);
                        }
                    }
                    else
                    {
                        // The device has not 16-bit address, so add it to the 64-bit map.
                        remotesBy64BitAddr.AddOrUpdate(addr64, remoteDevice, (k, v) => remoteDevice);
                        return(remoteDevice);
                    }
                }
            }

            // If the device has not 64-bit address, check if it has 16-bit address.
            if (addr16 != null && !addr16.Equals(XBee16BitAddress.UNKNOWN_ADDRESS))
            {
                // The device has 16-bit address, so look in the 64-bit map.
                ICollection <RemoteXBeeDevice> devices = remotesBy64BitAddr.Values;
                foreach (RemoteXBeeDevice d in devices)
                {
                    XBee16BitAddress a = Get16BitAddress(d);
                    if (a != null && a.Equals(addr16))
                    {
                        devInNetwork = d;
                        break;
                    }
                }
                // Check if the device exists in the 64-bit map.
                if (devInNetwork != null)
                {
                    // The device exists in the 64-bit map, so update the reference and return it.
                    logger.DebugFormat("{0}Existing device '{1}' in network.", localDevice.ToString(), devInNetwork.ToString());
                    devInNetwork.UpdateDeviceDataFrom(remoteDevice);
                    return(devInNetwork);
                }
                else
                {
                    // The device does not exist in the 64-bit map, so look in the 16-bit map.
                    if (remotesBy16BitAddr.TryGetValue(addr16, out devInNetwork))
                    {
                        // The device exists in the 16-bit map, so update the reference and return it.
                        logger.DebugFormat("{0}Existing device '{1}' in network.", localDevice.ToString(), devInNetwork.ToString());
                        devInNetwork.UpdateDeviceDataFrom(remoteDevice);
                        return(devInNetwork);
                    }
                    else
                    {
                        // The device does not exist in the 16-bit map, so add it.
                        remotesBy16BitAddr.AddOrUpdate(addr16, remoteDevice, (k, v) => remoteDevice);
                        return(remoteDevice);
                    }
                }
            }

            // If the device does not contain a valid address, return null.
            logger.ErrorFormat("{0}Remote device '{1}' cannot be added: 64-bit and 16-bit addresses must be specified.",
                               localDevice.ToString(), remoteDevice.ToString());
            return(null);
        }