core/src/main/java/org/apache/ftpserver/command/impl/EPSV.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.ftpserver.command.impl;

import java.io.IOException;
import java.net.InetSocketAddress;

import org.apache.ftpserver.DataConnectionException;
import org.apache.ftpserver.command.AbstractCommand;
import org.apache.ftpserver.ftplet.FtpReply;
import org.apache.ftpserver.ftplet.FtpRequest;
import org.apache.ftpserver.impl.FtpIoSession;
import org.apache.ftpserver.impl.FtpServerContext;
import org.apache.ftpserver.impl.LocalizedFtpReply;
import org.apache.ftpserver.impl.ServerDataConnectionFactory;

/**
 * <strong>Internal class, do not use directly.</strong>
 * 
 * The EPSV command requests that a server listen on a data port and wait for a
 * connection. The EPSV command takes an optional argument. The response to this
 * command includes only the TCP port number of the listening connection. The
 * format of the response, however, is similar to the argument of the EPRT
 * command. This allows the same parsing routines to be used for both commands.
 * In addition, the format leaves a place holder for the network protocol and/or
 * network address, which may be needed in the EPSV response in the future. The
 * response code for entering passive mode using an extended address MUST be
 * 229.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 */
public class EPSV extends AbstractCommand {

    /**
     * Execute command.
     */
    public void execute(final FtpIoSession session,
            final FtpServerContext context, final FtpRequest request)
            throws IOException {

        // reset state variables
        session.resetState();

        // set data connection
        ServerDataConnectionFactory dataCon = session.getDataConnection();

        try {
            InetSocketAddress dataConAddress = dataCon
                    .initPassiveDataConnection();
            // get connection info
            int servPort = dataConAddress.getPort();

            // send connection info to client
            String portStr = "|||" + servPort + '|';
            session.write(LocalizedFtpReply.translate(session, request, context,
                    229, "EPSV", portStr));

        } catch (DataConnectionException e) {
            session
                    .write(LocalizedFtpReply.translate(session, request, context,
                            FtpReply.REPLY_425_CANT_OPEN_DATA_CONNECTION,
                            "EPSV", null));
            return;
        }
    }
}