Lib/ftplib.py

Source:

cpython 3.14 @ ab2d84fe1023/Lib/ftplib.py ↗

ftplib implements the FTP protocol (RFC 959) client. It handles control connections, data connections (both active and passive mode), and the full command set. FTP_TLS adds explicit TLS via the AUTH TLS command.

Map

Lines	Symbol	Role
1-80	Constants, Error* exceptions	FTP exception hierarchy
81-250	FTP.__init__, connect, login, quit	Session management
251-450	sendcmd, getresp, getmultiline	Command/response exchange
451-650	retrbinary, retrlines, storbinary, storlines	Data transfers
651-750	nlst, mlsd, mlst, dir, rename, delete, mkd, rmd, cwd, pwd	File system commands
751-870	FTP_TLS, FTP.set_pasv	TLS support; passive mode

Reading

Control connection and response parsing

# CPython: Lib/ftplib.py:194 FTP.getresp
def getresp(self):
    resp = self.getmultiline()
    ...
    c = resp[:1]
    if c in {'1', '2', '3'}:
        return resp
    if c == '4':
        raise error_temp(resp)
    if c == '5':
        raise error_perm(resp)
    raise error_proto(resp)

FTP response codes: 1xx = positive preliminary, 2xx = positive completion, 3xx = positive intermediate, 4xx = transient negative, 5xx = permanent negative.

Passive mode data connection

# CPython: Lib/ftplib.py:386 FTP.makeport (active mode)
# CPython: Lib/ftplib.py:400 FTP.makepasv (passive mode)
def makepasv(self):
    host, port = parse227(self.sendcmd('PASV'))
    return host, port

Passive mode (PASV) is the default; the server opens a port and the client connects to it. Active mode (PORT) requires the server to connect back to the client, which is blocked by most firewalls.

retrbinary

# CPython: Lib/ftplib.py:470 FTP.retrbinary
def retrbinary(self, cmd, callback, blocksize=8192, rest=None):
    ...
    conn = self.transfercmd(cmd, rest)
    with conn:
        while 1:
            data = conn.recv(blocksize)
            if not data:
                break
            callback(data)
    return self.voidresp()

Issues a RETR command, opens the data connection, and calls callback(data) for each received chunk. The caller accumulates the data.

gopy notes

Status: not yet ported. Low priority; FTP is mostly legacy. Go's github.com/jlaffaye/ftp provides a compatible client if needed. A gopy port would use net.Dial for the control connection and a separate net.Dial for each data transfer.