Sprinting Using Double W While PVP Stops

I have found that while in single player sprinting with Double W (which I find so much easier to use) while fighting/pvping mobs like zombies. I can keep my sprint. Then in multiplayer servers I can't do so. It just sprints and as soon at I try or hit a player/mob it goes back to just walking and it really annoying when it comes to strafing. I have tested this on many of the servers i use and it has come with the same problem. {Please tell me if this is suppose to happen or if it is a problem.}