Each protocol or service runs on a default listening port: UDP 69 (TFTP), TCP 80 (HTTP), TCP 21 (FTP), and TCP 22 (SFTP). If Transfer cannot start one of these services, it’s likely that a macOS’s built-in or a third-party server for that protocol is already running, which prevents Transfer from starting the service. To resolve this issue, stop or disable the server process that’s conflicting with Transfer.

Below you can find instructions to disable file transfer services that come with macOS and may conflict with Transfer. To disable a third-party server, please refer to the software’s user manual.

Once you have disabled the conflicting server, click the Retry button on Transfer to restart the service or relaunch Transfer. If the problem continues, a different server application may be using the protocol’s listening port, and you need to stop it so you can use the protocol with Transfer.

TFTP

To stop and permanently disable the macOS’s TFTP server you will need admin privileges. Open Terminal and run the following two commands:

sudo launchctl stop com.apple.tftpd
sudo launchctl unload -F /System/Library/LaunchDaemons/tftp.plist

HTTP

To stop and permanently disable the macOS’s HTTP server you will need admin privileges. Open Terminal and run the following two commands:

sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist

FTP

Older versions of macOS provide a FTP server that’s enabled when you turn File Sharing on. To stop and permanently disable the macOS’s FTP server, you will need to disable file sharing using FTP. Go to System Preferences > Sharing and turn File Sharing off, or select File Sharing and click Options, then deselect “Share Files and Folders using FTP.”

SFTP

To stop and permanently disable the macOS’s SFTP server, you will need to disable Remote Login, as SFTP is a subsystem of SSH, which is the service that macOS uses to allow you to log in to your Mac remotely. To disable Remote Login, open System Preferences > Sharing and turn Remote Login off.