Package snow: is there any way to check if a cluster is "acticve"

Is there a 'proper' way of checking if cluster is active. For example, I create a cluster called .PBcluster

str(.PBcluster)

List of 4
  $ :List of 3
   ..$ con :Classes 'sockconn', 'connection'  atomic [1:1] 3
   .. .. ..- attr(*, "conn_id")=<externalptr>
   ..$ host: chr "localhost"
   ..$ rank: int 1
   ..- attr(*, "class")= chr "SOCKnode"
  $ :List of 3
....

Then I stop it with

stopCluster(.PBcluster)
.PBcluster

[[1]]
$con
Error in summary.connection(x) : invalid connection

str(.PBcluster)

List of 4
  $ :List of 3
   ..$ con :Classes 'sockconn', 'connection'  atomic [1:1] 3
   .. .. ..- attr(*, "conn_id")=<externalptr>
   ..$ host: chr "localhost"
   ..$ rank: int 1
   ..- attr(*, "class")= chr "SOCKnode"

- but is there a way in which I can check if the cluster is active??

Regards
S?ren