最近有个项目用到ftp上传，然后我在github上面找了一个叫android-upload-service的库，一开始连接的是家里NAS上的ftp没有问题，后来部署了服务器，无论是pureftp还是vsftp死活连接不上，有点坑，于是把源码拉下来看了一下，它是封装了Apache的Commons Net库，debug进去发现FTPUploadTask里面的ftpClient在调用connect之后就报超时异常，看样子是配置问题，经过逐一排查，发现是ftpClient.setAutodetectUTF8(true)导致，直接注销掉就行了，FTPUploadTask的upload函数如下

@Override
    protected void upload() throws Exception {
        try {
            if (ftpParams.useSSL) {
                String secureProtocol = ftpParams.secureSocketProtocol;

                if (secureProtocol == null || secureProtocol.isEmpty())
                    secureProtocol = FTPUploadTaskParameters.DEFAULT_SECURE_SOCKET_PROTOCOL;

                ftpClient = new FTPSClient(secureProtocol, ftpParams.implicitSecurity);

                Logger.debug(LOG_TAG, "Created FTP over SSL (FTPS) client with "
                        + secureProtocol + " protocol and "
                        + (ftpParams.implicitSecurity ? "implicit security" : "explicit security"));

            } else {
                ftpClient = new FTPClient();
            }

            ftpClient.setBufferSize(UploadService.BUFFER_SIZE);
            ftpClient.setCopyStreamListener(this);
            ftpClient.setDefaultTimeout(ftpParams.connectTimeout);
            ftpClient.setConnectTimeout(ftpParams.connectTimeout);
            ftpClient.setAutodetectUTF8(true);//注销掉这一行

            Logger.debug(LOG_TAG, "Connect timeout set to " + ftpParams.connectTimeout + "ms");

            Logger.debug(LOG_TAG, "Connecting to " + params.serverUrl
                                  + ":" + ftpParams.port + " as " + ftpParams.username);
            ftpClient.connect(params.serverUrl, ftpParams.port);

            if (!FTPReply.isPositiveCompletion(ftpClient.getReplyCode())) {
                throw new Exception("Can't connect to " + params.serverUrl
                                    + ":" + ftpParams.port
                                    + ". The server response is: " + ftpClient.getReplyString());
            }

            if (!ftpClient.login(ftpParams.username, ftpParams.password)) {
                throw new Exception("Error while performing login on " + params.serverUrl
                                    + ":" + ftpParams.port
                                    + " with username: " + ftpParams.username
                                    + ". Check your credentials and try again.");
            }

            // to prevent the socket timeout on the control socket during file transfer,
            // set the control keep alive timeout to a half of the socket timeout
            int controlKeepAliveTimeout = ftpParams.socketTimeout / 2 / 1000;

            ftpClient.setSoTimeout(ftpParams.socketTimeout);
            ftpClient.setControlKeepAliveTimeout(controlKeepAliveTimeout);
            ftpClient.setControlKeepAliveReplyTimeout(controlKeepAliveTimeout * 1000);

            Logger.debug(LOG_TAG, "Socket timeout set to " + ftpParams.socketTimeout
                         + "ms. Enabled control keep alive every " + controlKeepAliveTimeout + "s");

            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            ftpClient.setFileTransferMode(ftpParams.compressedFileTransfer ?
                                          FTP.COMPRESSED_TRANSFER_MODE : FTP.STREAM_TRANSFER_MODE);

            // this is needed to calculate the total bytes and the uploaded bytes, because if the
            // request fails, the upload method will be called again
            // (until max retries is reached) to retry the upload, so it's necessary to
            // know at which status we left, to be able to properly notify firther progress.
            calculateUploadedAndTotalBytes();

            String baseWorkingDir = ftpClient.printWorkingDirectory();
            Logger.debug(LOG_TAG, "FTP default working directory is: " + baseWorkingDir);

            Iterator<UploadFile> iterator = new ArrayList<>(params.files).iterator();
            while (iterator.hasNext()) {
                UploadFile file = iterator.next();

                if (!shouldContinue)
                    break;

                uploadFile(baseWorkingDir, file);
                addSuccessfullyUploadedFile(file);
                iterator.remove();
            }

            // Broadcast completion only if the user has not cancelled the operation.
            if (shouldContinue) {
                broadcastCompleted(new ServerResponse(UploadTask.TASK_COMPLETED_SUCCESSFULLY,
                                   UploadTask.EMPTY_RESPONSE, null));
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (ftpClient.isConnected()) {
                try {
                    Logger.debug(LOG_TAG, "Logout and disconnect from FTP server: "
                            + params.serverUrl + ":" + ftpParams.port);
                    ftpClient.logout();
                    ftpClient.disconnect();
                } catch (Exception exc) {
                    Logger.error(LOG_TAG, "Error while closing FTP connection to: "
                            + params.serverUrl + ":" + ftpParams.port, exc);
                }
            }
            ftpClient = null;
        }
    }