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  /*
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  * distributed under the License is distributed on an "AS IS" BASIS,
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 package org.apache.commons.net.bsd;
 
 
 import  org.apache.commons.net.io.SocketInputStream;

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 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 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 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 getErrorStream() . You can specify that a separate connection should be created for standard error by setting the boolean separateErrorStream parameter of rcommand() to true . The standard input of the remote process can be written to through the output stream returned by getOutputStream() .

See also:
org.apache.commons.net.SocketClient
RExecClient
RLoginClient
 
 
 public class RCommandClient extends RExecClient
 {
    
The default rshell port. Set to 514 in BSD Unix.
 
     public static final int DEFAULT_PORT = 514;

    
The smallest port number an rcmd client may use. By BSD convention this number is 512.
 
    public static final int MIN_CLIENT_PORT = 512;

    
The largest port number an rcmd client may use. By BSD convention this number is 1023.
    public static final int MAX_CLIENT_PORT = 1023;
    // Overrides method in RExecClient in order to implement proper
    // port number limitations.
    @Override
    {
        int localPort;
        ServerSocket server;
        Socket socket;
        localPort = ;
        server = null// Keep compiler from barfing
        for (localPort = localPort >= ; --localPort)
        {
            try
            {
                server = _serverSocketFactory_.createServerSocket(localPort, 1,
                         getLocalAddress());
                break// got a socket
            }
            catch (SocketException e)
            {
                continue;
            }
        }
        if (server == null) {
            throw new BindException("All ports in use.");
        }
        _output_.write(Integer.toString(server.getLocalPort()).getBytes("UTF-8")); // $NON-NLS
        _output_.write();
        _output_.flush();
        socket = server.accept();
        server.close();
        if (isRemoteVerificationEnabled() && !verifyRemote(socket))
        {
            socket.close();
            throw new IOException(
                "Security violation: unexpected connection attempt by " +
                socket.getInetAddress().getHostAddress());
        }
        return (new SocketInputStream(socketsocket.getInputStream()));
    }

    
The default RCommandClient constructor. Initializes the default port to DEFAULT_PORT .
    public RCommandClient()
    {
    }


    
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, _connectAction_() is called to perform connection initialization actions.

Parameters:
host The remote host.
port The port to connect to on the remote host.
localAddr The local address to use.
Throws:
SocketException If the socket timeout could not be set.
BindException If all acceptable rshell ports are in use.
IOException If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
    public void connect(InetAddress hostint portInetAddress localAddr)
    {
        int localPort;
        localPort = ;
        for (localPort = localPort >= ; --localPort)
        {
            try
            {
                _socket_ =
                    _socketFactory_.createSocket(hostportlocalAddrlocalPort);
            }
            catch (BindException be) {
                continue;
            }
            catch (SocketException e)
            {
                continue;
            }
            break;
        }
        if (localPort < ) {
            throw new BindException("All ports in use or insufficient permssion.");
        }
        _connectAction_();
    }



    
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, _connectAction_() is called to perform connection initialization actions.

Parameters:
host The remote host.
port The port to connect to on the remote host.
Throws:
SocketException If the socket timeout could not be set.
BindException If all acceptable rshell ports are in use.
IOException If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
    @Override
    public void connect(InetAddress hostint port)
    {
        connect(hostport, InetAddress.getLocalHost());
    }


    
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, _connectAction_() is called to perform connection initialization actions.

Parameters:
hostname The name of the remote host.
port The port to connect to on the remote host.
Throws:
SocketException If the socket timeout could not be set.
BindException If all acceptable rshell ports are in use.
IOException If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
UnknownHostException If the hostname cannot be resolved.
    @Override
    public void connect(String hostnameint port)
    {
        connect(InetAddress.getByName(hostname), port, InetAddress.getLocalHost());
    }


    
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, _connectAction_() is called to perform connection initialization actions.

Parameters:
hostname The remote host.
port The port to connect to on the remote host.
localAddr The local address to use.
Throws:
SocketException If the socket timeout could not be set.
BindException If all acceptable rshell ports are in use.
IOException If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
    public void connect(String hostnameint portInetAddress localAddr)
    {
        connect(InetAddress.getByName(hostname), portlocalAddr);
    }


    
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, _connectAction_() is called to perform connection initialization actions.

Parameters:
host The remote host.
port The port to connect to on the remote host.
localAddr The local address to use.
localPort The local port to use.
Throws:
SocketException If the socket timeout could not be set.
IOException If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
IllegalArgumentException If an invalid local port number is specified.
    @Override
    public void connect(InetAddress hostint port,
                        InetAddress localAddrint localPort)
    {
        if (localPort <  || localPort > ) {
            throw new IllegalArgumentException("Invalid port number " + localPort);
        }
        super.connect(hostportlocalAddrlocalPort);
    }


    
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, _connectAction_() is called to perform connection initialization actions.

Parameters:
hostname The name of the remote host.
port The port to connect to on the remote host.
localAddr The local address to use.
localPort The local port to use.
Throws:
SocketException If the socket timeout could not be set.
IOException If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
UnknownHostException If the hostname cannot be resolved.
IllegalArgumentException If an invalid local port number is specified.
    @Override
    public void connect(String hostnameint port,
                        InetAddress localAddrint localPort)
    {
        if (localPort <  || localPort > ) {
            throw new IllegalArgumentException("Invalid port number " + localPort);
        }
        super.connect(hostnameportlocalAddrlocalPort);
    }


    
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 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 setRemoteVerificationEnabled() .

Parameters:
localUsername The user account on the local machine that is requesting the command execution.
remoteUsername The account name on the server through which to execute the command.
command The command, including any arguments, to execute.
separateErrorStream True if you would like the standard error to be transmitted through a different stream than standard output. False if not.
Throws:
IOException If the rcommand() attempt fails. The exception will contain a message indicating the nature of the failure.
    public void rcommand(String localUsernameString remoteUsername,
                         String commandboolean separateErrorStream)
    throws IOException
    {
        rexec(localUsernameremoteUsernamecommandseparateErrorStream);
    }


    
Same as rcommand(localUsername, remoteUsername, command, false);
    public void rcommand(String localUsernameString remoteUsername,
                         String command)
    throws IOException
    {
        rcommand(localUsernameremoteUsernamecommandfalse);
    }
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