FTP

426 Connection Closed

Connection closed; transfer aborted. The data connection was closed unexpectedly during a file transfer.

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When You See This Code

When a file transfer is interrupted due to a network timeout, client disconnect, or the data connection dropping mid-transfer.

How to Fix

Retry the transfer. If it keeps failing, check network stability, increase timeout values, and verify there are no firewalls killing idle connections.

Specification

View RFC / Specification →

Compare With

110 Restart Marker Reply 120 Service Ready Soon 125 Data Connection Open 150 File Status OK 200 Command OK 202 Command Superfluous 211 System Status 212 Directory Status 213 File Status 214 Help Message 215 System Type 220 Service Ready

Guides

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

Debugging Scenarios

550 File Unavailable — Permission Denied Beginner

Specifications

RFC 959 File Transfer Protocol (FTP)

Glossary

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

Frequently Asked Questions

What is FTP 426 Connection Closed?

Connection closed; transfer aborted. The data connection was closed unexpectedly during a file transfer.

When do you see FTP 426 Connection Closed?

When a file transfer is interrupted due to a network timeout, client disconnect, or the data connection dropping mid-transfer.

How to fix FTP 426 Connection Closed?

Retry the transfer. If it keeps failing, check network stability, increase timeout values, and verify there are no firewalls killing idle connections.