If user want to open new channel they have to have the option to close the current one.
Update the error text.
Remove the channel field as it is not necessary.
privateconststringInvalidRegistrationError="Unable to open a channel with the specified name. The most probable cause is that you have already registered a channel with a different name.";
privateconststringInvalidRegistrationError="Unable to open a channel with the specified name. The most probable cause is that you have already registered a channel with a different name. Call unregister(old-channel-name) or uninstall and redeploy your application.";
privateconststringMissingChannelError="Couldn't find a channel with the specified name.";