Friday, February 17, 2012

Experience with SFTP Clients


Say you want to transfer files over a network in a secured mannar.Here comes the usecase of SFTP[Secure File Transfer Protocol].SFTP is a secured protocol which is an extention of the Secure Shell protocol(SSH) provides capabilities as file accessing,file transferring and file management.

This protocol encrypts both commands and data and ensure not transmitting of passwords and sensitive information over the network.SFTP functionality is similar to FTP,but since FTP uses a different protocol,you cannot use FTP client to talk to an SFTP server.

To use SFTP capabilities,you can try out either graphical SFTP client or either at the command line.

At command line -[In Unix or Mac OS environment]

  • Start a SFTP session by 'sftp username@hostname'
  • Then enter the password when prompted.
  • Then with using sftp commands you can try-out file operations.[To get SFTP commands type 'help']
When you are using command line to SFTP operations you'll mostly remember about SCP protocol usage.But compared to SCP,there are advantages in SFTP protocol.
  • SCP provides only file-transfering,but SFTP provides more operations on remote files.
  • SFTP client has extra capabilities compared to a SCP client as directory listing,remote file removal and resume interrupted transfers.
Graphical SFTP Clients

There are several SFTP clients that can be try-out and could be found from internet.But note that the FTP only clients coudn't be use to access to SFTP.I tried out two such graphical SFTP clients,which are able to get freely.

1. WinSCP- This is an free client support all SFTP,SCP and FTP.It's main function is file transfering between a local and a remote computer.Adding to that it provides scripting support and file manager functionality.You can find more info on [1].

2.gFTP-This is a free multithreaded file transfer client for *NIX based machines.You can install the client from ubuntu software center.For more info refer [2].




[1]http://winscp.net/eng/index.php
[2]http://www.gftp.org/











Wednesday, February 8, 2012

WSO2 ESB Proxy Services


If you are have ever try-out WSO2 ESB[1],you are quite familiar with WSO2 ESB proxy services.
A proxy service is a some kind of virtual service,which fronts an existing actual service end-point and which is hosted under WSO2 ESB.

Clients can send requests for proxy services hosted in ESB,as the client sees that service hosted in ESB without knowing of actual service end-point.Such proxy service has own WSDL which can be view from '?wsdl' parameter.

Advantage of such a proxy service is that proxy services can mediate the sending messages to the actual service,before they are delivered to the actual end-point and can mediate the responses before those reach the client.

There are several templates for proxy services as below and you can get more info on proxy services from [2].
  • Pass Through Proxy- Create a simple proxy service on a specified endpoint. This proxy service does not perform any processing on the messages that pass through the proxy.
  • Secure Proxy-Create a proxy service with WS-Security engaged in-order to expose an existing service with WS-Security.
  • WSDL Based Proxy-Create a proxy service from a WSDL of an existing web service.Endpoint information is extracted from such remotely hosted WSDL of an actual service.
  • Log and Forward Proxy-Create a proxy service which logs all the incoming requests and forwards them to a given end-point.[If necessary responses coming back from back-end service can be logged before routing them to the client.]
  • Transformer Proxy-Create a proxy service, which can transform requests and responses based on a specified XSLT configurations,where user is trying to expose a scenario from an existing service in a different message format.
  • Custom Proxy-Create a proxy service in which customize each aspects of a proxy including sequences,endpoints,transports.

The reason why I wrote this blog is to highlight a property which used in each proxy service template definitions.That's property.

In WSO2 ESB UI,when adding a new proxy service as in the image ,you'll see that you have to add proxy service name,the end-point of relevant actual service and then add publish WSDL options.

In this 'publish WSDL options', you can keep without pointing to any wsdl while setting that option 'none' or pointing to a wsdl url either from registry[keep option as 'Pick from Registry'] or from browser[keep option as 'Specify source url'] or adding to a inline wsdl[keep option as 'Specify in-line'].Once you set this 'publish WSDL options' from UI,you'll see the entry corresponding to wsdl options has defined in the proxy service source view definition accordingly as below.






The use of the above WSDL option is that,if a user likes to publish the actual back-end service WSDL into proxy service wsdl without hiding it,you can set above WSDL options with pointing to the url of actual service's WSDL.If a user don't want to publish the actual back-end service's wsdl from proxy service,that user can keep the wsdl options as 'none',without pointing to any wsdl.

[1] http://wso2.com/products/enterprise-service-bus/
[2]http://wso2.org/project/esb/java/4.0.3/docs/samples/proxy_samples.html