503
FTP
503 Bad Sequence
Bad sequence of commands. The command is valid but was sent in the wrong order relative to other commands.
このコードが表示される場合
When you skip a required step, like sending PASS before USER, or RNTO without first sending RNFR.
解決方法
Follow the correct command sequence. Common sequences: USER then PASS for login, RNFR then RNTO for rename, PASV then RETR for transfer.
比較対象
ガイド
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
用語集
Status Code
TLS Handshake
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Port Number
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FTP Reply Code
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FTP Chroot Jail
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rsync
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FTP over TLS (RFC 4217)
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