public int receiveFile()

in src/main/java/org/apache/commons/net/tftp/TFTPClient.java [126:233]
94 lines of code
19 McCabe index (conditional complexity)

    public int receiveFile(final String fileName, final int mode, OutputStream output, InetAddress host, final int port) throws IOException {
        int bytesRead = 0;
        int lastBlock = 0;
        int block = 1;
        int hostPort = 0;
        int dataLength = 0;

        totalBytesReceived = 0;

        if (mode == ASCII_MODE) {
            output = new FromNetASCIIOutputStream(output);
        }

        TFTPPacket sent = new TFTPReadRequestPacket(host, port, fileName, mode);
        final TFTPAckPacket ack = new TFTPAckPacket(host, port, 0);

        beginBufferedOps();

        boolean justStarted = true;
        try {
            do { // while more data to fetch
                bufferedSend(sent); // start the fetch/send an ack
                boolean wantReply = true;
                int timeouts = 0;
                do { // until successful response
                    try {
                        final TFTPPacket received = bufferedReceive();
                        // The first time we receive we get the port number and
                        // answering host address (for hosts with multiple IPs)
                        final int recdPort = received.getPort();
                        final InetAddress recdAddress = received.getAddress();
                        if (justStarted) {
                            justStarted = false;
                            if (recdPort == port) { // must not use the control port here
                                final TFTPErrorPacket error = new TFTPErrorPacket(recdAddress, recdPort, TFTPErrorPacket.UNKNOWN_TID, "INCORRECT SOURCE PORT");
                                bufferedSend(error);
                                throw new IOException("Incorrect source port (" + recdPort + ") in request reply.");
                            }
                            hostPort = recdPort;
                            ack.setPort(hostPort);
                            if (!host.equals(recdAddress)) {
                                host = recdAddress;
                                ack.setAddress(host);
                                sent.setAddress(host);
                            }
                        }
                        // Comply with RFC 783 indication that an error acknowledgment
                        // should be sent to originator if unexpected TID or host.
                        if (host.equals(recdAddress) && recdPort == hostPort) {
                            switch (received.getType()) {

                            case TFTPPacket.ERROR:
                                TFTPErrorPacket error = (TFTPErrorPacket) received;
                                throw new IOException("Error code " + error.getError() + " received: " + error.getMessage());
                            case TFTPPacket.DATA:
                                final TFTPDataPacket data = (TFTPDataPacket) received;
                                dataLength = data.getDataLength();
                                lastBlock = data.getBlockNumber();

                                if (lastBlock == block) { // is the next block number?
                                    try {
                                        output.write(data.getData(), data.getDataOffset(), dataLength);
                                    } catch (final IOException e) {
                                        error = new TFTPErrorPacket(host, hostPort, TFTPErrorPacket.OUT_OF_SPACE, "File write failed.");
                                        bufferedSend(error);
                                        throw e;
                                    }
                                    ++block;
                                    if (block > 65535) {
                                        // wrap the block number
                                        block = 0;
                                    }
                                    wantReply = false; // got the next block, drop out to ack it
                                } else { // unexpected block number
                                    discardPackets();
                                    if (lastBlock == (block == 0 ? 65535 : block - 1)) {
                                        wantReply = false; // Resend last acknowledgemen
                                    }
                                }
                                break;

                            default:
                                throw new IOException("Received unexpected packet type (" + received.getType() + ")");
                            }
                        } else { // incorrect host or TID
                            final TFTPErrorPacket error = new TFTPErrorPacket(recdAddress, recdPort, TFTPErrorPacket.UNKNOWN_TID, "Unexpected host or port.");
                            bufferedSend(error);
                        }
                    } catch (final SocketException | InterruptedIOException e) {
                        if (++timeouts >= maxTimeouts) {
                            throw new IOException("Connection timed out.");
                        }
                    } catch (final TFTPPacketException e) {
                        throw new IOException("Bad packet: " + e.getMessage());
                    }
                } while (wantReply); // waiting for response

                ack.setBlockNumber(lastBlock);
                sent = ack;
                bytesRead += dataLength;
                totalBytesReceived += dataLength;
            } while (dataLength == TFTPPacket.SEGMENT_SIZE); // not eof
            bufferedSend(sent); // send the final ack
        } finally {
            endBufferedOps();
        }
        return bytesRead;
    }