[ns] Simulation error

[Maurizio Bellemo]

Hi,
does anyone know why i get this error simulating?

ns: _o2021 sendData IP_BROADCAST:
    (_o2021 cmd line 1)
    invoked from within
"_o2021 cmd sendData IP_BROADCAST"
    invoked from within
"catch "$self cmd $args" ret"
    invoked from within
"if [catch "$self cmd $args" ret] {
set cls [$self info class]
global errorInfo
set savedInfo $errorInfo
error "error when calling class $cls: $args" $..."
    (procedure "_o2021" line 2)
    (SplitObject unknown line 2)
    invoked from within
"_o2021 sendData IP_BROADCAST"

Thank you
Maurizio