This chapter describes how two File Transfer Service applications interact.
There are several ways the OMG File Transfer Service can be used. Below one scenario is visualized:
VFS
represents.
In this scenario it is the local disk or the NFS.
CORBA
requests to determine whether or not they can communicate. If the
File Transfer Service's have one, or more, Transport Protocol
in common the data
will be streamed using this protocol. The cosFileTransfer application currently supports
TCP/IP
and SSL
.
Which type of file system the VFS
is supposed to represent is determined
by the options given when creating it, which is also how one determine which
Transport Protocol
to use. Hence, the source and target VFS
described above
can be started by invoking, respectively, the following operations:
1> SVFS = cosFileTransferApp:create_VFS('FTP', [], Host, 21, [{protocol, tcp}]), 2> TVFS = cosFileTransferApp:create_VFS({'NATIVE', 'cosFileTransferNATIVE_file'}, [], OtherHost, 0, [{protocol, tcp}]),
Naturally can any combination of VFS
-types be used and it is also possible
to use own drivers, i.e., {'NATIVE', 'MyDriver'}
.
After creating necessary VFS's
we can login in and perform operations
on files and directories residing on each file system.
To be able to use SSL
as transport protocol a few configuration
parameters must be set. The required parameters depend on if Orber is
the target or/and the source ORB. However, the SSL_CERT_FILE variable
must be defined in both cases.
Setting of a CA certificate file with an option does not work due to weaknesses in the SSLeay package. A work-around in the ssl application is to set the OS environment variable SSL_CERT_FILE before SSL is started. However, then the CA certificate file will be global for all connections (both incomming and outgoing calls).
The following three configuration variables can be used to configure cosFileTransfer's SSL target behavior.
There also exist a number of API functions for accessing the values of these variables:
Below is the list of configuration variables used when cosFileTransfer act as the source application.
There also exist a number of API functions for accessing the values of these variables in the client processes: