public void start()

in httpcore5-testing/src/main/java/org/apache/hc/core5/testing/SocksProxy.java [68:194]
117 lines of code
19 McCabe index (conditional complexity)

        public void start() {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        final DataInputStream input = new DataInputStream(socket.getInputStream());
                        final DataOutputStream output = new DataOutputStream(socket.getOutputStream());
                        final Socket target = establishConnection(input, output);
                        remote = target;

                        final Thread t1 = pumpStream(input, target.getOutputStream());
                        final Thread t2 = pumpStream(target.getInputStream(), output);
                        try {
                            t1.join();
                        } catch (final InterruptedException ignored) {
                        }
                        try {
                            t2.join();
                        } catch (final InterruptedException ignored) {
                        }
                    } catch (final IOException ignored) {
                    } finally {
                        parent.cleanupSocksProxyHandler(SocksProxyHandler.this);
                    }
                }

                private Socket establishConnection(final DataInputStream input, final DataOutputStream output) throws IOException {
                    final int clientVersion = input.readUnsignedByte();
                    if (clientVersion != VERSION_5) {
                        throw new IOException("SOCKS implementation only supports version 5");
                    }
                    final int nMethods = input.readUnsignedByte();
                    for (int i = 0; i < nMethods; i++) {
                        input.readUnsignedByte(); // auth method
                    }
                    // response
                    output.writeByte(VERSION_5);
                    output.writeByte(0); // no auth method
                    output.flush();

                    input.readUnsignedByte(); // client version again
                    final int command = input.readUnsignedByte();
                    if (command != COMMAND_CONNECT) {
                        throw new IOException("SOCKS implementation only supports CONNECT command");
                    }
                    input.readUnsignedByte(); // reserved

                    final String targetHost;
                    final byte[] targetAddress;
                    final int addressType = input.readUnsignedByte();
                    switch (addressType) {
                        case InetAddressUtils.IPV4:
                            targetHost = null;
                            targetAddress = new byte[4];
                            for (int i = 0; i < targetAddress.length; i++) {
                                targetAddress[i] = input.readByte();
                            }
                            break;
                        case InetAddressUtils.IPV6:
                            targetHost = null;
                            targetAddress = new byte[16];
                            for (int i = 0; i < targetAddress.length; i++) {
                                targetAddress[i] = input.readByte();
                            }
                            break;
                        case ATYP_DOMAINNAME:
                            final int length = input.readUnsignedByte();
                            final StringBuilder domainname = new StringBuilder();
                            for (int i = 0; i < length; i++) {
                                domainname.append((char) input.readUnsignedByte());
                            }
                            targetHost = domainname.toString();
                            targetAddress = null;
                            break;
                        default:
                            throw new IOException("Unsupported address type: " + addressType);
                    }

                    final int targetPort = input.readUnsignedShort();
                    final Socket target;
                    if (targetHost != null) {
                        target = new Socket(targetHost, targetPort);
                    } else {
                        target = new Socket(InetAddress.getByAddress(targetAddress), targetPort);
                    }

                    output.writeByte(VERSION_5);
                    output.writeByte(0); /* success */
                    output.writeByte(0); /* reserved */
                    final byte[] localAddress = target.getLocalAddress().getAddress();
                    if (localAddress.length == 4) {
                        output.writeByte(InetAddressUtils.IPV4);
                    } else if (localAddress.length == 16) {
                        output.writeByte(InetAddressUtils.IPV6);
                    } else {
                        throw new IOException("Unsupported localAddress byte length: " + localAddress.length);
                    }
                    output.write(localAddress);
                    output.writeShort(target.getLocalPort());
                    output.flush();

                    return target;
                }

                private Thread pumpStream(final InputStream input, final OutputStream output) {
                    final Thread t = new Thread(() -> {
                        final byte[] buffer = new byte[1024 * 8];
                        try {
                            while (true) {
                                final int read = input.read(buffer);
                                if (read < 0) {
                                    break;
                                }
                                output.write(buffer, 0, read);
                                output.flush();
                            }
                        } catch (final IOException ignored) {
                        } finally {
                            shutdown();
                        }
                    });
                    t.start();
                    return t;
                }

            }).start();
        }