| org.apache.commons.net.bsd.RExecClient
 org.apache.commons.net.bsd.RCommandClient
All known Subclasses: org.apache.commons.net.bsd.RLoginClient,
| RCommandClient | | public class RCommandClient extends RExecClient (Code) | | RCommandClient is very similar to
org.apache.commons.net.bsd.RExecClient ,
from which it is derived, and implements the rcmd() facility that
first appeared in 4.2BSD Unix. rcmd() is the facility used by the rsh
(rshell) and other commands to execute a command on another machine
from a trusted host without issuing a password. The trust relationship
between two machines is established by the contents of a machine's
/etc/hosts.equiv file and a user's .rhosts file. These files specify
from which hosts and accounts on those hosts rcmd() requests will be
accepted. The only additional measure for establishing trust is that
all client connections must originate from a port between 512 and 1023.
Consequently, there is an upper limit to the number of rcmd connections
that can be running simultaneously. The required ports are reserved
ports on Unix systems, and can only be bound by a
process running with root permissions (to accomplish this rsh, rlogin,
and related commands usualy have the suid bit set). Therefore, on a
Unix system, you will only be able to successfully use the RCommandClient
class if the process runs as root. However, there is no such restriction
on Windows95 and some other systems. The security risks are obvious.
However, when carefully used, rcmd() can be very useful when used behind
a firewall.
As with virtually all of the client classes in org.apache.commons.net, this
class derives from SocketClient. But it overrides most of its connection
methods so that the local Socket will originate from an acceptable
rshell port. The way to use RCommandClient is to first connect
to the server, call the
RCommandClient.rcommand rcommand() method,
and then
fetch the connection's input, output, and optionally error streams.
Interaction with the remote command is controlled entirely through the
I/O streams. Once you have finished processing the streams, you should
invoke
org.apache.commons.net.bsd.RExecClient.disconnect disconnect() to clean up properly.
By default the standard output and standard error streams of the
remote process are transmitted over the same connection, readable
from the input stream returned by
org.apache.commons.net.bsd.RExecClient.getInputStream getInputStream() . However, it is
possible to tell the rshd daemon to return the standard error
stream over a separate connection, readable from the input stream
returned by
org.apache.commons.net.bsd.RExecClient.getErrorStream getErrorStream() . You
can specify that a separate connection should be created for standard
error by setting the boolean separateErrorStream
parameter of
RCommandClient.rcommand rcommand() to true .
The standard input of the remote process can be written to through
the output stream returned by
org.apache.commons.net.bsd.RExecClient.getOutputStream getOutputStream() .
author:
Daniel F. Savarese
See Also: org.apache.commons.net.SocketClient
See Also: RExecClient
See Also: RLoginClient |
| Field Summary | |
| final public static int | DEFAULT_PORT
The default rshell port. | | final public static int | MAX_CLIENT_PORT
The largest port number an rcmd client may use. | | final public static int | MIN_CLIENT_PORT
The smallest port number an rcmd client may use. |
| Constructor Summary | |
| public | RCommandClient()
The default RCommandClient constructor. |
| Method Summary | |
| InputStream | _createErrorStream()
| | public void | connect(InetAddress host, int port, InetAddress localAddr)
Opens a Socket connected to a remote host at the specified port and
originating from the specified local address using a port in a range
acceptable to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
host - The remote host.
Parameters:
port - The port to connect to on the remote host.
Parameters:
localAddr - The local address to use.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. | | public void | connect(InetAddress host, int port)
Opens a Socket connected to a remote host at the specified port and
originating from the current host at a port in a range acceptable
to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
host - The remote host.
Parameters:
port - The port to connect to on the remote host.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. | | public void | connect(String hostname, int port)
Opens a Socket connected to a remote host at the specified port and
originating from the current host at a port in a range acceptable
to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
hostname - The name of the remote host.
Parameters:
port - The port to connect to on the remote host.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. | | public void | connect(String hostname, int port, InetAddress localAddr)
Opens a Socket connected to a remote host at the specified port and
originating from the specified local address using a port in a range
acceptable to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
hostname - The remote host.
Parameters:
port - The port to connect to on the remote host.
Parameters:
localAddr - The local address to use.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. | | public void | connect(InetAddress host, int port, InetAddress localAddr, int localPort)
Opens a Socket connected to a remote host at the specified port and
originating from the specified local address and port. | | public void | connect(String hostname, int port, InetAddress localAddr, int localPort)
Opens a Socket connected to a remote host at the specified port and
originating from the specified local address and port. | | public void | rcommand(String localUsername, String remoteUsername, String command, boolean separateErrorStream)
Remotely executes a command through the rshd daemon on the server
to which the RCommandClient is connected. | | public void | rcommand(String localUsername, String remoteUsername, String command)
|
| DEFAULT_PORT | | final public static int DEFAULT_PORT(Code) | | The default rshell port. Set to 514 in BSD Unix.
|
| MAX_CLIENT_PORT | | final public static int MAX_CLIENT_PORT(Code) | | The largest port number an rcmd client may use. By BSD convention
this number is 1023.
|
| MIN_CLIENT_PORT | | final public static int MIN_CLIENT_PORT(Code) | | The smallest port number an rcmd client may use. By BSD convention
this number is 512.
|
| RCommandClient | | public RCommandClient()(Code) | | The default RCommandClient constructor. Initializes the
default port to DEFAULT_PORT .
|
| connect | | public void connect(InetAddress host, int port, InetAddress localAddr) throws SocketException, BindException, IOException(Code) | | Opens a Socket connected to a remote host at the specified port and
originating from the specified local address using a port in a range
acceptable to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
host - The remote host.
Parameters:
port - The port to connect to on the remote host.
Parameters:
localAddr - The local address to use.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. In mostcases you will only want to catch IOException since SocketException isderived from it. |
| connect | | public void connect(InetAddress host, int port) throws SocketException, IOException(Code) | | Opens a Socket connected to a remote host at the specified port and
originating from the current host at a port in a range acceptable
to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
host - The remote host.
Parameters:
port - The port to connect to on the remote host.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. In mostcases you will only want to catch IOException since SocketException isderived from it. |
| connect | | public void connect(String hostname, int port) throws SocketException, IOException(Code) | | Opens a Socket connected to a remote host at the specified port and
originating from the current host at a port in a range acceptable
to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
hostname - The name of the remote host.
Parameters:
port - The port to connect to on the remote host.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. In mostcases you will only want to catch IOException since SocketException isderived from it.
exception:
UnknownHostException - If the hostname cannot be resolved. |
| connect | | public void connect(String hostname, int port, InetAddress localAddr) throws SocketException, IOException(Code) | | Opens a Socket connected to a remote host at the specified port and
originating from the specified local address using a port in a range
acceptable to the BSD rshell daemon.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
hostname - The remote host.
Parameters:
port - The port to connect to on the remote host.
Parameters:
localAddr - The local address to use.
exception:
SocketException - If the socket timeout could not be set.
exception:
BindException - If all acceptable rshell ports are in use.
exception:
IOException - If the socket could not be opened. In mostcases you will only want to catch IOException since SocketException isderived from it. |
| connect | | public void connect(InetAddress host, int port, InetAddress localAddr, int localPort) throws SocketException, IOException, IllegalArgumentException(Code) | | Opens a Socket connected to a remote host at the specified port and
originating from the specified local address and port. The
local port must lie between MIN_CLIENT_PORT and
MAX_CLIENT_PORT or an IllegalArgumentException will
be thrown.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
host - The remote host.
Parameters:
port - The port to connect to on the remote host.
Parameters:
localAddr - The local address to use.
Parameters:
localPort - The local port to use.
exception:
SocketException - If the socket timeout could not be set.
exception:
IOException - If the socket could not be opened. In mostcases you will only want to catch IOException since SocketException isderived from it.
exception:
IllegalArgumentException - If an invalid local port numberis specified. |
| connect | | public void connect(String hostname, int port, InetAddress localAddr, int localPort) throws SocketException, IOException, IllegalArgumentException(Code) | | Opens a Socket connected to a remote host at the specified port and
originating from the specified local address and port. The
local port must lie between MIN_CLIENT_PORT and
MAX_CLIENT_PORT or an IllegalArgumentException will
be thrown.
Before returning,
org.apache.commons.net.SocketClient._connectAction_ _connectAction_() is called to perform connection initialization actions.
Parameters:
hostname - The name of the remote host.
Parameters:
port - The port to connect to on the remote host.
Parameters:
localAddr - The local address to use.
Parameters:
localPort - The local port to use.
exception:
SocketException - If the socket timeout could not be set.
exception:
IOException - If the socket could not be opened. In mostcases you will only want to catch IOException since SocketException isderived from it.
exception:
UnknownHostException - If the hostname cannot be resolved.
exception:
IllegalArgumentException - If an invalid local port numberis specified. |
| rcommand | | public void rcommand(String localUsername, String remoteUsername, String command, boolean separateErrorStream) throws IOException(Code) | | Remotely executes a command through the rshd daemon on the server
to which the RCommandClient is connected. After calling this method,
you may interact with the remote process through its standard input,
output, and error streams. You will typically be able to detect
the termination of the remote process after reaching end of file
on its standard output (accessible through
RCommandClient.getInputStream getInputStream() . Disconnecting
from the server or closing the process streams before reaching
end of file will not necessarily terminate the remote process.
If a separate error stream is requested, the remote server will
connect to a local socket opened by RCommandClient, providing an
independent stream through which standard error will be transmitted.
The local socket must originate from a secure port (512 - 1023),
and rcommand() ensures that this will be so.
RCommandClient will also do a simple security check when it accepts a
connection for this error stream. If the connection does not originate
from the remote server, an IOException will be thrown. This serves as
a simple protection against possible hijacking of the error stream by
an attacker monitoring the rexec() negotiation. You may disable this
behavior with
org.apache.commons.net.bsd.RExecClient.setRemoteVerificationEnabled setRemoteVerificationEnabled() .
Parameters:
localUsername - The user account on the local machine that isrequesting the command execution.
Parameters:
remoteUsername - The account name on the server through which toexecute the command.
Parameters:
command - The command, including any arguments, to execute.
Parameters:
separateErrorStream - True if you would like the standard errorto be transmitted through a different stream than standard output.False if not.
exception:
IOException - If the rcommand() attempt fails. The exceptionwill contain a message indicating the nature of the failure. |
| rcommand | | public void rcommand(String localUsername, String remoteUsername, String command) throws IOException(Code) | | Same as
rcommand(localUsername, remoteUsername, command, false);
|
|
|