How does FTP technically work on glasses hardware?

On standalone Android compute units, FTP uses the device's WiFi to establish standard TCP connections to FTP servers. The protocol operates identically to any Android device — control channel on port 21, passive data connections for transfers.

Should I use FTP or SFTP on glasses?

SFTP for security-sensitive transfers (credentials are encrypted). FTP is fine for home network use with a dedicated limited account. SFTP adds slight overhead but significantly improves security.

What FTP servers work best with glasses?

Any standard FTP server: Synology/QNAP NAS, vsftpd, ProFTPD, FileZilla Server. Configure passive mode and set generous timeouts. Simple folder structures work best given glasses' interface constraints.

Can glasses upload files to FTP servers?

Yes. Compute units can upload files (sensor logs, captured photos, AR data) to FTP servers. Audio-only glasses can't directly upload, but the paired phone can upload content from the phone's storage.

FTP Protocol on Smart Glasses — Server File Access for Wearable Computing

FTP Protocol Specifics for Smart Glasses

This page covers the technical aspects of FTP protocol usage on smart glasses hardware — connection mechanics, server configuration for optimal glasses compatibility, and protocol-level considerations specific to wearable computing devices.

The FTP protocol itself is device-agnostic — it works identically whether the client is a desktop, phone, or glasses compute unit. The differences lie in the hardware constraints: input methods, display limitations, battery sensitivity, and WiFi reliability.

Protocol Operation on Glasses Hardware

Network Stack

Glasses compute units running Android have a standard TCP/IP stack:

WiFi radio provides network connectivity (2.4/5 GHz depending on hardware)
Standard socket connections support FTP's dual-channel design
Control channel (port 21) maintains session state
Data channels (passive mode dynamic ports) carry file transfers

FTP Session Flow on Glasses

1. TCP connect to server:21
2. Receive server banner (220 response)
3. USER username → 331 response
4. PASS password → 230 response (logged in)
5. TYPE I (binary mode) → 200 response
6. PASV → 227 response (data port assigned)
7. LIST (directory listing) → data transfer
8. PASV → 227 (new data port)
9. RETR filename → file download begins
10. QUIT → session ends

Each operation follows standard FTP RFC 959 protocol. AnExplorer handles all protocol negotiation transparently.

Passive Mode Requirement

Passive mode (PASV) is essential for glasses. Reasons:

Glasses are behind NAT (home router) — active mode needs server-to-client connection which NAT blocks
Glasses may have restricted incoming connection support
All modern FTP implementations should use passive mode anyway
AnExplorer defaults to passive mode

Server-side passive port configuration:

Define a port range (e.g., 50000-51000)
Open this range in firewall if applicable
Configure masquerade address if server is behind NAT (for remote access)

Server Configuration for Glasses

Recommended server settings

For optimal compatibility with glasses compute units:

# vsftpd example configuration
pasv_enable=YES
pasv_min_port=50000
pasv_max_port=51000
idle_session_timeout=120
data_connection_timeout=120
utf8_filesystem=YES
ascii_upload_enable=NO
local_enable=YES

Key settings explained:

Passive mode enabled: Required for glasses behind NAT
Generous timeouts: Glasses may be slower to navigate; avoid premature disconnection
UTF-8 support: Handles international filenames
Binary mode default: Media files must transfer as binary
Local user authentication: Standard username/password access

User account setup

Create a dedicated glasses user:

# Create user with restricted shell
useradd -m -s /usr/sbin/nologin glasses-sync
echo "glasses-sync:secure-password" | chpasswd

# Create content directory
mkdir -p /home/glasses-sync/{audio,assets,configs}
chown -R glasses-sync:glasses-sync /home/glasses-sync

Or on NAS (GUI-based):

Control Panel → Users → Create
Name: "glasses-sync"
Set permissions: read-only on media shares, read-write on upload shares
Enable FTP access for this user

Folder structure optimization

Design for limited-display navigation:

/glasses-sync/
├── audio/           ← First-level: content types
│   ├── new/         ← Second-level: status-based
│   └── favorites/   ← Quick access to known content
├── ar-assets/
│   ├── current/     ← Latest versions only
│   └── archive/     ← Old versions (rarely accessed)
└── upload/          ← For glasses-to-server transfers

Principle: Maximum 2 levels deep for glasses browsing. Keep "latest" or "current" folders at the top level for minimal navigation.

Transfer Protocol Details

Binary vs. ASCII

Always use binary transfer mode for glasses:

Audio files (MP3, FLAC, AAC): must be binary
Images: must be binary
AR assets (GLB, textures): must be binary
Only plain text files could use ASCII (but binary works for text too)

AnExplorer sets binary mode by default. No user configuration needed.

Resume support (REST command)

FTP resume allows interrupted transfers to continue:

If WiFi drops mid-transfer, reconnect and resume from last byte
Server must support REST command (most do)
Particularly important for glasses where WiFi stability may vary
AnExplorer attempts resume automatically for interrupted downloads

Transfer size limits

No inherent FTP protocol size limit. Practical limits for glasses:

Available storage on device (check before large transfers)
Battery life during transfer (large files take time)
WiFi session stability (longer transfers = more chance of interruption)

Protocol Comparison for Glasses

Aspect	FTP	SFTP	SMB	WebDAV
Port	21	22	445	443/80
Encryption	None	Full	Optional	Optional (HTTPS)
Authentication	USER/PASS	Keys or password	User/pass	User/pass
Streaming capable	No (download only)	No	Yes	Partial
Resume support	Yes (REST)	Yes	Limited	Partial
Best for	Bulk transfer	Secure transfer	Media streaming	Cloud access
Firewall friendly	Moderate	Good	Poor (remote)	Excellent

For glasses audio: SMB for streaming, FTP/SFTP for downloads. For glasses assets: FTP for bulk deployment, SFTP for sensitive content.

Performance on Glasses Hardware

CPU impact

FTP itself has minimal CPU overhead (unlike SFTP which requires encryption/decryption). On glasses compute units with limited processing power, FTP's lower CPU demands mean: