220
FTP
220 Service Ready
Service ready for new user. This is the greeting message sent by the FTP server when a client first connects.
Khi bạn thấy mã này
Immediately upon connecting to an FTP server. This is the welcome banner confirming the server is accepting connections.
Cách khắc phục
No fix needed — the server is ready. Proceed with USER and PASS commands to authenticate.
Đặc tả
So sánh với
Hướng dẫn
FTP Reply Codes: Understanding File Transfer Responses
DNS & Networking
TCP Three-Way Handshake and Connection Lifecycle
DNS & Networking
Essential Network Debugging Tools: ping, traceroute, mtr, and tcpdump
DNS & Networking
RFC 959: FTP Protocol Deep Dive
Protocol Deep Dives
TLS 1.3: Faster, Simpler, More Secure
Protocol Deep Dives
Migrating from FTP to SFTP: A Complete Transition Guide
Migration & Upgrades
HTTP Access Log Management: Rotation, Parsing, and Analysis
Production Infrastructure
Đặc tả
Thuật ngữ
Status Code
TLS Handshake
TCP/IP
Three-Way Handshake
Port Number
Firewall
Proxy Server (Forward Proxy)
Socket
Request-Response Model
RFC (Request for Comments)
Connection-Oriented
Half-Duplex
Text vs Binary Protocol
FTP Active Mode
FTP Passive Mode
FTP Control Channel
FTP Data Channel
SFTP (SSH File Transfer Protocol)
FTPS (FTP Secure)
FTP Reply Code
FTP Anonymous Access
FTP Transfer Mode (ASCII vs Binary)
FTP Resume (REST Command)
SCP (Secure Copy Protocol)
FTP Chroot Jail
WebDAV (Web Distributed Authoring and Versioning)
rsync
FTP MLSD (Machine-Readable Listing)
FTP NAT Traversal
Transfer Integrity
FTP over TLS (RFC 4217)
File Locking
Bandwidth Throttling
TLS Versions