Version mismatch shouldn’t totally prevent a user from at least attempting to connect to a server. It should instead be a warning window, but let them proceed if they wish. Blocking them seems a bit useless, especially when some versions might have compiling problems on some systems at least the problem version can have a fallback state, thus allowing users an attempted connection. Same should occur between dev and release versions.
Is there any reason why users should not be allowed to at least attempt to connect? Will it melt their computer? Will it cause WW3?