private Socket openDataSecureConnection()

in src/main/java/org/apache/commons/net/ftp/FTPSClient.java [688:820]
88 lines of code
31 McCabe index (conditional complexity)

    private Socket openDataSecureConnection(final String command, final String arg) throws IOException {
        if (getDataConnectionMode() != ACTIVE_LOCAL_DATA_CONNECTION_MODE && getDataConnectionMode() != PASSIVE_LOCAL_DATA_CONNECTION_MODE) {
            return null;
        }

        final boolean isInet6Address = getRemoteAddress() instanceof Inet6Address;

        final Socket socket;
        Socket sslSocket = null;
        final int soTimeoutMillis = DurationUtils.toMillisInt(getDataTimeout());
        if (getDataConnectionMode() == ACTIVE_LOCAL_DATA_CONNECTION_MODE) {
            // if no activePortRange was set (correctly) -> getActivePort() = 0
            // -> new ServerSocket(0) -> bind to any free local port
            try (final ServerSocket server = _serverSocketFactory_.createServerSocket(getActivePort(), 1, getHostAddress())) {
                // Try EPRT only if remote server is over IPv6, if not use PORT,
                // because EPRT has no advantage over PORT on IPv4.
                // It could even have the disadvantage,
                // that EPRT will make the data connection fail, because
                // today's intelligent NAT Firewalls are able to
                // substitute IP addresses in the PORT command,
                // but might not be able to recognize the EPRT command.
                if (isInet6Address) {
                    if (!FTPReply.isPositiveCompletion(eprt(getReportHostAddress(), server.getLocalPort()))) {
                        return null;
                    }
                } else if (!FTPReply.isPositiveCompletion(port(getReportHostAddress(), server.getLocalPort()))) {
                    return null;
                }

                if ((getRestartOffset() > 0) && !restart(getRestartOffset())) {
                    return null;
                }

                if (!FTPReply.isPositivePreliminary(sendCommand(command, arg))) {
                    return null;
                }

                // For now, let's just use the data timeout value for waiting for
                // the data connection. It may be desirable to let this be a
                // separately configurable value. In any case, we really want
                // to allow preventing the accept from blocking indefinitely.
                if (soTimeoutMillis >= 0) {
                    server.setSoTimeout(soTimeoutMillis);
                }
                socket = server.accept();

                // Ensure the timeout is set before any commands are issued on the new socket
                if (soTimeoutMillis >= 0) {
                    socket.setSoTimeout(soTimeoutMillis);
                }
                if (getReceiveDataSocketBufferSize() > 0) {
                    socket.setReceiveBufferSize(getReceiveDataSocketBufferSize());
                }
                if (getSendDataSocketBufferSize() > 0) {
                    socket.setSendBufferSize(getSendDataSocketBufferSize());
                }
            }
        } else { // We must be in PASSIVE_LOCAL_DATA_CONNECTION_MODE

            // Try EPSV command first on IPv6 - and IPv4 if enabled.
            // When using IPv4 with NAT it has the advantage
            // to work with more rare configurations.
            // E.g. if FTP server has a static PASV address (external network)
            // and the client is coming from another internal network.
            // In that case the data connection after PASV command would fail,
            // while EPSV would make the client succeed by taking just the port.
            final boolean attemptEPSV = isUseEPSVwithIPv4() || isInet6Address;
            if (attemptEPSV && epsv() == FTPReply.ENTERING_EPSV_MODE) {
                _parseExtendedPassiveModeReply(_replyLines.get(0));
            } else {
                if (isInet6Address) {
                    return null; // Must use EPSV for IPV6
                }
                // If EPSV failed on IPV4, revert to PASV
                if (pasv() != FTPReply.ENTERING_PASSIVE_MODE) {
                    return null;
                }
                _parsePassiveModeReply(_replyLines.get(0));
            }

            if (getProxy() != null) {
                socket = new Socket(getProxy());
            } else {
                socket = _socketFactory_.createSocket();
            }

            if (getReceiveDataSocketBufferSize() > 0) {
                socket.setReceiveBufferSize(getReceiveDataSocketBufferSize());
            }
            if (getSendDataSocketBufferSize() > 0) {
                socket.setSendBufferSize(getSendDataSocketBufferSize());
            }
            if (getPassiveLocalIPAddress() != null) {
                socket.bind(new InetSocketAddress(getPassiveLocalIPAddress(), 0));
            }

            // For now, let's just use the data timeout value for waiting for
            // the data connection. It may be desirable to let this be a
            // separately configurable value. In any case, we really want
            // to allow preventing the accept from blocking indefinitely.
            if (soTimeoutMillis >= 0) {
                socket.setSoTimeout(soTimeoutMillis);
            }

            socket.connect(new InetSocketAddress(getPassiveHost(), getPassivePort()), connectTimeout);

            if (getProxy() != null) {
                sslSocket = context.getSocketFactory().createSocket(socket, getPassiveHost(), getPassivePort(), true);
            }

            if ((getRestartOffset() > 0) && !restart(getRestartOffset())) {
                closeSockets(socket, sslSocket);
                return null;
            }

            if (!FTPReply.isPositivePreliminary(sendCommand(command, arg))) {
                closeSockets(socket, sslSocket);
                return null;
            }
        }

        if (isRemoteVerificationEnabled() && !verifyRemote(socket)) {
            // Grab the host before we close the socket to avoid NET-663
            final InetAddress socketHost = socket.getInetAddress();

            closeSockets(socket, sslSocket);

            throw new IOException(
                    "Host attempting data connection " + socketHost.getHostAddress() + " is not same as server " + getRemoteAddress().getHostAddress());
        }

        return getProxy() != null ? sslSocket : socket;
    }