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PowerShell NetCmdlets -debug

Its easy to forget about the –debug parameter, but a lot of times it can be very helpful, especially with NetCmdlets where in many cases –debug will output the protocol interface (the “PITrail” as we call it at /n software) of the connection.  The PITrail includes a trail of communication between the cmdlet and the remote host it is talking to.

Rob emailed me to ask for help diagnosing a 425 error he was getting when using the NetCmdlets get-ftp cmdlet.  As I described to Rob, in a nutshell the 425 problem happens because the FTP client (the cmdlet in this case) is unable to open a TCP data connection (for transferring data like file directory listings or file contents) on the ip and port that the server told it to use. 

Adding the -debug parameter to the get-ftp call, I can see what ip and port the server is telling me to connect to:

PS C:\> get-ftp -server 10.0.1.1 -user myusername –password ******* -debug                                                    
DEBUG: VerbsCommon.Get-FTP started processing.                                                                          
                                                                                                                        
Confirm                                                                                                                 
Continue with this operation?                                                                                           
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend  [?] Help (default is "Y"): a                                    
DEBUG: Info: Connecting to FTP server.                                                                                  
DEBUG: Server: 220 (vsFTPd 2.0.4)                                                                                       
DEBUG: Client: USER myusername                                                                                                
DEBUG: Server: 331 Please specify the password.                                                                         
DEBUG: Client: PASS *******                                                                                             
DEBUG: Server: 230 Login successful.                                                                                    
DEBUG: Client: PASV                                                                                                     
DEBUG: Server: 227 Entering Passive Mode (10,0,1,1,225,79)                                                              
DEBUG: Client: LIST                                                                                                     
DEBUG: Server: 150 Here comes the directory listing.                                                                    
                                                                                                                                                                                                                                                
DirEntry : drwx------    2 1036     100           144 Nov 16  2007 test.txt                                                   
FileName : test.txt                                                                                                           
FileSize : 144                                                                                                          
FileTime : Nov 16 2007                                                                                                  
IsDir    : True                                                                                                         
                                                                                                                        
DirEntry : -rw-------    1 1036     100            14 Jun 20 14:56 test2.txt             
FileName : test2.txt                                                                     
FileSize : 14                                                                                                           
FileTime : Jun 20 14:56                                                                                                 
IsDir    : False
In Rob's case, his 415 error happened right after the LIST command.  By using –debug, we were able to see without a doubt that the server was actually sending a valid ip and port in its response, but that port simply wasn’t open on the firewall guarding the server machine. 

The firewall *should* have been able to see the port that the server chose and open it up, but I guess this particular firewall just isn’t that smart.  Anyway, Rob was able to correctly configure a smaller passive port range in IIS FTP and sync that range with his firewall.

Related:  FTP Error 425,
FTPS Through NAT

Print | posted on Thursday, September 11, 2008 4:41 PM

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