As Knobtviker said, you have to be a "root" user, this is what I did and it may be another better way to do it but it worked (i guess):

1. In terminal: devel-su
2. Password: root me
3. Change password: passwd user
4. New password: user (type it twice)
5. Open WinScp and syncronize with SDK connection
6. In terminal: cd /opt/waxmppplugin/bin/wazapp enter
7. then: chmod o+w protocoltreenode.py
8. Open the file /opt/waxmppplugin/bin/wazapp/protocoltreenode.py in WinScp

9. In my case, I did not replace the whole file, just this part:

def readInt16(self,i,socketOnly=0):
intTop = i.read(socketOnly);
intBot = i.read(socketOnly);
#Utilities.debug(str(intTop)+"------------"+str(intBot));
value = (intTop << 8) + intBot;
if value is not None:
return value;
else:
return "";

10. Save and exit