How close a conection UDP beetwen two computers and re-open it again?

I am using this: fclose(udpA), to close the conecction, then use: delete udpA, to delete the object. But when I want conect to the other computer again I create the object UDP again and use fopen(udpA) , But I get this error : Error using icinterface/fopen (line 83) Unsuccessful open: Unrecognized Windows Sockets error: 0: Cannot bind

Error in red (line 4) fopen(udpA)

I'm desasperate, please someone help me, when I want to conect again I have to close all my MATLAB and open it again .