grunt serve Fatal error: Port 35729 is already in use by another process.

y@y:~$ lsof | grep 35729
grunt     18194                y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
Optimizin 18194 18195          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
v8:Sweepe 18194 18196          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
v8:Sweepe 18194 18197          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
v8:Sweepe 18194 18198          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
grunt     18194 18295          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
grunt     18194 18296          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
grunt     18194 18297          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
grunt     18194 18298          y   13u     IPv6             117971       0t0      TCP *:35729 (LISTEN)
y@y:~$ ps -ef | grep grunt
y         8705  8501  0 17:54 pts/27   00:00:00 grep --color=auto grunt
y        18194  4497  3 08:57 pts/11   00:20:06 grunt                                     
y@y:~$ kill -9 18194
y@y:~$ ps -ef | grep grunt
y         8715  8501  0 17:54 pts/27   00:00:00 grep --color=auto grunt
y@y:~$ lsof | grep 35729
y@y:~$