Synchronet v3.19b-Win32 (install) has been released (Jan-2022).

You can donate to the Synchronet project using PayPal.

FTP Server

The Synchronet FTP Server is a native server (written in C) which supports the FTP and FTPS TCP protocols for file transfer.

Anonymous Logins

So-called “Anonymous FTP” logins (client-login using the user-ID “anonymous”, “ftp”, or “guest”) are supported when the BBS user database contains a “Guest” user account.

Traditionally, the user's email address is given as the password during “anonymous FTP” logins. To block specific email addresses from being used in this manner, add the address(es) to your text/email.can file.

Sysop Access

To login with system operator access, the user must login with a user account that has a security level of 90 or higher and provide a password of “<user-pass>:<sys-pass>” where <user-pass> is the user's personal password and <sys-pass> is the system password as configured in SCFG->System.

A successful sysop login will generate a login message stating “Sysop access granted”.

230-Sysop access granted.

Logging in with just a personal password will give the user/sysop normal (non-sysop) access.

Sysop access allows the FTP user to mount local file systems and execute administrative commands via the FTP server.

When logged-in with sysop access, the user has access to the following additional FTP commands:


Local File System Access

Local file system access is enabled by default. Local file system access can be disabled with the NO_LOCAL_FSYS Options flag in the [FTP] section of the ctrl/sbbs.ini file or by un-checking the “Local File System” checkbox in the Synchronet Control Panel->FTP->Configure dialog.

When local file system access is enabled, a user with sysop access can “mount” a local file system using the FTP CWD or XCWD commands to change to “local:<path>” where <path> is the local file system directory to mount. An alternative method of mounting the local file system is to use the SMNT <local-dir> command. To re-mount (switch back to) the BBS file system, the SMNT bbs: command can be used or CWD/XCWD command with a path beginning with bbs:.


The Synchronet FTP server can be configured via SCFG:Servers->FTP Server:

║                  FTP Server                  ║
║ │Enabled                       Yes           ║
║ │Log Level                     Informational ║
║ │Network Interfaces  , ::   ║
║ │Control Port                  21, Data: 20  ║
║ │Passive Interface (IPv4)       ║
║ │Passive Port Range            1024 - 65535  ║
║ │Auto-generate Index File      00index       ║
║ │QWK Message Packet Transfers  Yes           ║
║ │QWK Message Packet Timeout    10 minutes    ║
║ │Max Clients                   100           ║
║ │Max Inactivity                5 minutes     ║
║ │Max Concurrent Connections    Unlimited     ║
║ │Sysop File System Access      Yes           ║
║ │Allow Bounce Transfers        No            ║
║ │Lookup Client Hostname        Yes           ║
║ │Failed Login Attempts...                    ║

... via SBBSCTRL:FTP->Configure:

... or via manual editing of the [FTP] section of the ctrl/sbbs.ini file.


The [ftp] section of the ctrl/sbbs.ini file supports the following configuration settings (key = value lines):

Key Default Value Description
AutoStart true Automatically start up the server (manual is only supported in sbbsctrl)
Interface [global] Comma-separated list of IPv4 and IPv6 network interfaces to listen on for incoming TCP connections
Port 21 Control TCP Port
MaxClients 10 Maximum number of simultaneous incoming TCP sessions supported
MaxConcurrentConnections 0 Maximum number of concurrent connections from the same IP address (0 = unlimited)
MaxInactivity 300 Maximum amount of TCP session inactivity before timeout and disconnection (in seconds)
QwkTimeout 600 Maximum amount of time to wait for QWK packet creation (in seconds)
SemFileCheckFrequency [global] Frequency (in seconds) of checks for semaphore files
MinFileSize 0 Minimum uploaded file size, in bytes (0 = no-minimum)
MaxFileSize 0 Maximum uploaded file size, in bytes (0 = no-maximum)
PasvIpAddress 0 IPv4 address to advertise for PASV client data connections (0 = auto)
PasvPortLow 1024 Lowest TCP port number to use for PASV data connections
PasvPortHigh 65535 Highest TCP port number to use for PASV data connections
HostName [global] DNS Hostname of server
IndexFileName 00index Filename to use for auto-generated downloadable file listings
AnswerSound WAV file to play (on Windows) when answering incoming connections
HangupSound WAV file to play (on Windows) when clients disconnect
HackAttemptSound WAV file to play (on Windows) upon detected suspected hack attempt
TempDirectory [global] Directory to use for temporary file storage
LogLevel [global] Minimum severity of log messages to be displayed / stored
BindRetryCount [global] Maximum number of TCP port bind attempts before failure
BindRetryDelay [global] Delay (in seconds) between TCP port bind retries
LoginAttempt* [global] Failed login attempt throttling / filtering / banning
Options ALLOW_INDX_FILE | ALLOW_QWK FTP server option flags (see below for details)


The Options key of the [ftp] section of the ctrl/sbbs.ini file supports the following option flags (separated by a | character):

Option Description
DEBUG_RX Log all received commands (Debug log level)
DEBUG_TX Log all transmissions (Debug log level)
DEBUG_DATA Log all DATA channel activity
INDEX_FILE Auto-generate index (listing) files for optional download
ALLOW_QWK Allow download/upload of QWK/REP packets
ALLOW_BOUNCE Allow authenticated non-guest/anonymous users to use FTP Bounce (FXP) functionality - not recommended
NO_LOCAL_FSYS Disable local file system access (for sysops)
KEEP_TEMP_FILES Don't delete temporary files, for debug purposes
LOOKUP_PASV_IP Resolve public IP address for PASV response
NO_HOST_LOOKUP Do not resolve/log hostnames of incoming TCP connections
NO_RECYCLE Do not allow this server to be automatically recycled by external event
MUTE Disable all sound (WAV) files from playing


You can create a list of file aliases that will appear in your FTP root directory for:

  • Quick and easy access to often downloaded user files
  • Static filenames that corresponds to a dynamically changing filenames
  • Download access to files on the local disk not in the BBS file database

Edit the file ctrl/ftpalias.cfg with a text editor (SBBSCTRL->FTP->Edit->Filename Aliases).

The ftpalias.cfg file format is one file or directory alias per line, in the form:

<alias>  <path>  [description]

The <alias> field is not case-sensitive and may not contain spaces. This is the filename that will appear in listing of your FTP root directory.

The <path> field is either the full path and filename to a file on a local file system (e.g. C:\DOCS\MYFILE.TXT or /docs/myfile.txt) or a virtual path to a file in the BBS file database. Virtual paths are specified as


where lib is the library short name, dir is the directory internal code and filename is the actual filename of the referenced file (may be the long filename, but may not contain spaces).

The [description] field is the optional description of the file that will be used in the dynamically generated Auto Index file (if you have this option enabled). Descriptions of “hidden” indicate files or directories that are not be included in listings.

Blank lines are ignored.

Lines beginning with a semicolon (;) character are considered comments and are ignored.

Example Alias:   bbs://main/sbbs/   Current version for SBBS for DOS

Display Files

The Synchronet FTP server can optionally send text files from your text directory to the FTP client/user under certain conditions:

Filename Description
ftplogin.txt Sent before the username and password is requested
ftphello.txt Sent upon successful login
ftpbadlogin.txt Sent upon unsuccessful login attempt
ftpbye.txt Sent upon logoff (before server acknowledgment of the QUIT command)

Supported Commands


See Also