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org.acplt.oncrpc
Class OncRpcHttpClient

java.lang.Object
  extended by org.acplt.oncrpc.OncRpcClient
      extended by org.acplt.oncrpc.OncRpcHttpClient

public class OncRpcHttpClient
extends OncRpcClient

ONC/RPC client which communicates with ONC/RPC servers over the network using the ISO/OSI level 7 application protocol HTTP as a tunnel.

Please note that currently no standard exists about how to tunnel XDR data over HTTP connections. There are a few solutions out there, but they are more or less incompatible due to the lack of an RFC. So I'm now adding yet another proprietary solution.

The protocol which is used here is rather simple and tries to be compatible with as much firewall systems as possible. For this to achieve, both the ONC/RPC calls as well as their replies are first base64 encoded, before they are sent through the tunnel. This way, calls and replies appear to be ordinary text documents of mime type "text/plain".

Calls will appear to be something like this, carrying redirection information. Note that we do not include ONC/RPC call information in the header section, as this is already included in the ONC/RPC call itself. So including it in the header would just make it easier to play games with the header. 

     CALL host name:port protocol TEA/1<CR><LF>
     B0D0EADSDEADBEEF...<CR><LF>
     ...<CR><LF>
     DEADBE==<CR><LF>

Replies do not carry the redirection head, but only the base64 encoded data of the ONC/RPC reply: 

     B0D0EADSDEADBEEF...<CR><LF>
     ...<CR><LF>
     DEADBE==<CR><LF>

The decoding from the base64 encoded data is carried out by the XdrHttpDecodingStream class.

I'm not using eecks-emm-ell on purpose (net yet). While it is surely fun to play with and it has its merits, just to create yet another RPC tunnel parsing XML is still too large an overhead to accept. Despite cynics pointing out that the Internet is already that slow so that XML overhead will not be visible at all, I nevertheless disagree. On the other hand, XML would be really fine to be misused for yet another proprietary and misguided ASCII, pardon UTF-8, data format... 

     <?xml version="1.0"?>
     <!DOCTYPE oncrpc-call SYSTEM "oncrpc-call.dtd">
     <oncrpc-call server="foo.bar.com" protocol="tcp">
         B0D0EADSDEADBEEF...<CR><LF>
         ...<CR><LF>
         DEADBE==<CR><LF>
     </oncrpc-call>

The answer then could be represented as follows: 

     <?xml version="1.0"?>
     <!DOCTYPE oncrpc-reply SYSTEM "oncrpc-reply.dtd">
     <oncrpc-reply>
         B0D0EADSDEADBEEF...<CR><LF>
         ...<CR><LF>
         DEADBE==<CR><LF>
     </oncrpc-reply>

So it should be fairly easy to switch over to XML if someone will insist on it. Reminds me of my Xmas lecture about "Internet Technologies -- Sacred Land of the Automation Industry?"...

See Also:
XdrHttpDecodingStream, HttpClientConnection

Field Summary
private  java.lang.String cgiHandlerPath
          Path of cgi program redirecting ONC/RPC calls to the appropriate ONC/RPC servers.
private  java.lang.String hostname
          DNS name of host where to contact HTTP server.
private  HttpClientConnection httpClient
          The HTTP client responsible for handling the HTTP connection.
private  int httpPort
          Port number where the HTTP server can be contacted.
private  java.lang.String oncrpcHostname
          DNS name of ONC/RPC server receiving the calls.
private  int oncrpcProtocol
          Transport protocol to be used by the other end of the tunnel to contact the ONC/RPC server.
private  XdrHttpDecodingStream receivingXdr
          XDR decoding stream used when receiving replies via an HTTP tunnel from an ONC/RPC server.
private  XdrBufferEncodingStream sendingXdr
          FIXME: use the right encoding stream! XDR encoding stream used for sending requests via UDP/IP to an ONC/RPC server.
 
Fields inherited from class org.acplt.oncrpc.OncRpcClient
auth, host, port, program, timeout, version, xid
 
Constructor Summary
OncRpcHttpClient(java.lang.String hostname, int httpPort, java.lang.String cgiHandlerPath, java.lang.String oncrpcHostname, int program, int version, int port, int protocol)
          Constructs a new OncRpcHttpClient object, which connects to the ONC/RPC server at host for calling remote procedures of the given { program, version }.
OncRpcHttpClient(java.lang.String hostname, java.lang.String cgiHandlerPath, java.lang.String oncrpcHostname, int program, int version, int port)
          Constructs a new OncRpcHttpClient object, which connects to the ONC/RPC server at host for calling remote procedures of the given { program, version }.
OncRpcHttpClient(java.lang.String hostname, java.lang.String cgiHandlerPath, java.lang.String oncrpcHostname, int program, int version, int port, int protocol)
          Constructs a new OncRpcHttpClient object, which connects to the ONC/RPC server at host for calling remote procedures of the given { program, version }.
 
Method Summary
 void call(int procedureNumber, int versionNumber, XdrAble params, XdrAble result)
          Calls a remote procedure on an ONC/RPC server.
 void close()
          Close the connection to an ONC/RPC server and free all network-related resources.
 java.lang.String getCharacterEncoding()
          Get the character encoding for (de-)serializing strings.
 java.lang.String getHostname()
          Returns the host name of the HTTP server we are connected to.
 int getHttpPort()
          Returns the port of the HTTP server we are connected to.
 void setCharacterEncoding(java.lang.String characterEncoding)
          Set the character encoding for (de-)serializing strings.
 
Methods inherited from class org.acplt.oncrpc.OncRpcClient
call, getAuth, getHost, getPort, getProgram, getTimeout, getVersion, newOncRpcClient, newOncRpcClient, nextXid, setAuth, setTimeout
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

hostname

private java.lang.String hostname
DNS name of host where to contact HTTP server. Note that we can not use an InetAddress here as we have to support virtual hosting, where several DNS names share the same IP address.

httpPort

private int httpPort
Port number where the HTTP server can be contacted.

cgiHandlerPath

private java.lang.String cgiHandlerPath
Path of cgi program redirecting ONC/RPC calls to the appropriate ONC/RPC servers.

oncrpcHostname

private java.lang.String oncrpcHostname
DNS name of ONC/RPC server receiving the calls.

oncrpcProtocol

private int oncrpcProtocol
Transport protocol to be used by the other end of the tunnel to contact the ONC/RPC server.

httpClient

private HttpClientConnection httpClient
The HTTP client responsible for handling the HTTP connection. It is a classic example of delegation, isn't it?

sendingXdr

private XdrBufferEncodingStream sendingXdr
FIXME: use the right encoding stream! XDR encoding stream used for sending requests via UDP/IP to an ONC/RPC server.

receivingXdr

private XdrHttpDecodingStream receivingXdr
XDR decoding stream used when receiving replies via an HTTP tunnel from an ONC/RPC server.

Constructor Detail

OncRpcHttpClient

public OncRpcHttpClient(java.lang.String hostname,
                        java.lang.String cgiHandlerPath,
                        java.lang.String oncrpcHostname,
                        int program,
                        int version,
                        int port)
                 throws OncRpcException,
                        java.io.IOException
Constructs a new OncRpcHttpClient object, which connects to the ONC/RPC server at host for calling remote procedures of the given { program, version }. At the other end of the HTTP tunnel, TCP/IP is used to call the ONC/RPC server.

Note that the HTTP connection is not build before the first ONC/RPC call is done through the call(int, int, org.acplt.oncrpc.XdrAble, org.acplt.oncrpc.XdrAble) method. The HTTP client tries to keep the connection alive but reconnects if necessary. Nevertheless, as it signals all failures, the caller has to handle reconnect situations -- but this is easy to achieve.

Parameters:
hostname - The DNS name of the host where the ONC/RPC server resides.
cgiHandlerPath - The path to the CGI Handler which will redirect ONC/RPC calls to the particular ONC/RPC servers.
oncrpcHostname - The DNS name of the ONC/RPC server to contact.
program - Program number of the ONC/RPC server to call.
version - Program version number.
port - The port number where the ONC/RPC server can be contacted. If 0, then the other end of the HTTP tunnel will try to ask the portmapper at host for the port number.
Throws:
OncRpcException - if an ONC/RPC error occurs.
java.io.IOException - if an I/O error occurs.

OncRpcHttpClient

public OncRpcHttpClient(java.lang.String hostname,
                        java.lang.String cgiHandlerPath,
                        java.lang.String oncrpcHostname,
                        int program,
                        int version,
                        int port,
                        int protocol)
                 throws OncRpcException,
                        java.io.IOException
Constructs a new OncRpcHttpClient object, which connects to the ONC/RPC server at host for calling remote procedures of the given { program, version }.

Note that the HTTP connection is not build before the first ONC/RPC call is done through the call(int, int, org.acplt.oncrpc.XdrAble, org.acplt.oncrpc.XdrAble) method. The HTTP client tries to keep the connection alive but reconnects if necessary. Nevertheless, as it signals all failures, the caller has to handle reconnect situations -- but this is easy to achieve.

Parameters:
hostname - The DNS name of the host where the ONC/RPC server resides.
cgiHandlerPath - The path to the CGI Handler which will redirect ONC/RPC calls to the particular ONC/RPC servers.
oncrpcHostname - The DNS name of the ONC/RPC server to contact.
program - Program number of the ONC/RPC server to call.
version - Program version number.
port - The port number where the ONC/RPC server can be contacted. If 0, then the other end of the HTTP tunnel will try to ask the portmapper at host for the port number.
protocol - Transport protocol to be used by the other end of the tunnel to call the ONC/RPC server.
Throws:
OncRpcException - if an ONC/RPC error occurs.
java.io.IOException - if an I/O error occurs.

OncRpcHttpClient

public OncRpcHttpClient(java.lang.String hostname,
                        int httpPort,
                        java.lang.String cgiHandlerPath,
                        java.lang.String oncrpcHostname,
                        int program,
                        int version,
                        int port,
                        int protocol)
                 throws OncRpcException,
                        java.io.IOException
Constructs a new OncRpcHttpClient object, which connects to the ONC/RPC server at host for calling remote procedures of the given { program, version }.

Note that the HTTP connection is not build before the first ONC/RPC call is done through the call(int, int, org.acplt.oncrpc.XdrAble, org.acplt.oncrpc.XdrAble) method. The HTTP client tries to keep the connection alive but reconnects if necessary. Nevertheless, as it signals all failures, the caller has to handle reconnect situations -- but this is easy to achieve.

Parameters:
hostname - The DNS name of the host where the ONC/RPC server resides.
httpPort - The port number where the HTTP server is to be contacted.
cgiHandlerPath - The path to the CGI Handler which will redirect ONC/RPC calls to the particular ONC/RPC servers.
oncrpcHostname - The DNS name of the ONC/RPC server to contact.
program - Program number of the ONC/RPC server to call.
version - Program version number.
port - The port number where the ONC/RPC server can be contacted. If 0, then the other end of the HTTP tunnel will try to ask the portmapper at host for the port number.
protocol - Transport protocol to be used by the other end of the tunnel to call the ONC/RPC server.
Throws:
OncRpcException - if an ONC/RPC error occurs.
java.io.IOException - if an I/O error occurs.
Method Detail

close

public void close()
           throws OncRpcException
Close the connection to an ONC/RPC server and free all network-related resources. Well -- at least hope, that the Java VM will sometimes free some resources. Sigh.

Overrides:
close in class OncRpcClient
Throws:
OncRpcException - if an ONC/RPC error occurs.

call

public void call(int procedureNumber,
                 int versionNumber,
                 XdrAble params,
                 XdrAble result)
          throws OncRpcException
Calls a remote procedure on an ONC/RPC server.

FIXME: timeout control?

Specified by:
call in class OncRpcClient
Parameters:
procedureNumber - Procedure number of the procedure to call.
versionNumber - Protocol version number.
params - The parameters of the procedure to call, contained in an object which implements the XdrAble interface.
result - The object receiving the result of the procedure call.
Throws:
OncRpcException - if an ONC/RPC error occurs.

setCharacterEncoding

public void setCharacterEncoding(java.lang.String characterEncoding)
Set the character encoding for (de-)serializing strings.

Specified by:
setCharacterEncoding in class OncRpcClient
Parameters:
characterEncoding - the encoding to use for (de-)serializing strings. If null, the system's default encoding is to be used.

getCharacterEncoding

public java.lang.String getCharacterEncoding()
Get the character encoding for (de-)serializing strings.

Specified by:
getCharacterEncoding in class OncRpcClient
Returns:
the encoding currently used for (de-)serializing strings. If null, then the system's default encoding is used.

getHostname

public java.lang.String getHostname()
Returns the host name of the HTTP server we are connected to.

Returns:
host name.

getHttpPort

public int getHttpPort()
Returns the port of the HTTP server we are connected to.

Returns:
port number.
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