Hello exception thrown while using rebex ssh

command that throw this exception runs every 1 seconds

 Rebex.Net.SshException was unhandled  
 Message=The channel has been closed.  
 Source=Rebex.Net.Ssh   StackTrace:
        at Rebex.Net.SshChannel.cDtmAOZ(Boolean ,
 cMbfbTZ , Object[] )
        at Rebex.Net.SshChannel.BoomUs(BBdsJfZ )
        at Rebex.Net.SshChannel.RequestExec(String
 command)
        at Rebex.Net.Ssh.StartCommand(String
 command)
        at Saigma_server_contoller.server.execute_periodic(String
 command, Int32 timeout) in
 D:\applications area\serverc\Saigma
 server contoller\Saigma server
 contoller\classes\server_connection.cs:line
 55
        at Saigma_server_contoller.controller.get_uptime()
 in D:\applications area\serverc\Saigma
 server contoller\Saigma server
 contoller\controller.cs:line 156
        at System.Threading.ThreadHelper.ThreadStart_Context(Object
 state)
        at System.Threading.ExecutionContext.Run(ExecutionContext
 executionContext, ContextCallback
 callback, Object state, Boolean
 ignoreSyncCtx)
        at System.Threading.ExecutionContext.Run(ExecutionContext
 executionContext, ContextCallback
 callback, Object state)
        at System.Threading.ThreadHelper.ThreadStart()
 InnerException: