Supported Protocols

The N: device supports multiple network protocols, each suited to different tasks. This page provides detailed information about each protocol, including its devicespec format, connection modes, and usage notes.

Protocol Summary

TCP

TCP (Transmission Control Protocol) provides reliable, ordered, stream-oriented communication between two hosts. The underlying TCP/IP stack handles retransmission, ordering, and error correction, making it ideal for applications where data integrity is critical.

Use Cases

• Telnet and BBS connections
• Raw terminal sessions
• Communicating with custom TCP services

Devicespec Format

Client Mode

N[x]:TCP://<HOST>[:PORT]/

Examples:

N:TCP://BBS.FOZZTEXX.COM:23/       Connect to a BBS on port 23
N:TCP://192.168.1.1:1234/           Connect to IP address on port 1234
N:TCP://MYSERVER:6502/              Connect to custom service

Server (Listening) Mode

N[x]:TCP://:<PORT>/

Opens a listening socket on the specified port. When a client connects, you must issue an ACCEPT command (XIO 41) to attach the incoming client to the N: device.

Example:

N:TCP://:6502/                      Listen for connections on port 6502

Limitations

Important: A maximum of 4 simultaneous TCP connections is supported. Attempting to open additional connections will return an error.

Connection Flow

flowchart TD
    A[OPEN N:TCP://host:port/] --> B{Client or Server?}
    B -->|Client| C[Connect to remote host]
    B -->|Server| D[Open listening socket]
    D --> E[Wait for incoming connection]
    E --> F["XIO 41 (ACCEPT)"]
    F --> G[Client attached to N: device]
    C --> G
    G --> H[Read / Write data]
    H --> I[CLOSE]

UDP

UDP (User Datagram Protocol) provides connectionless, datagram-oriented communication. Unlike TCP, UDP does not guarantee delivery, ordering, or duplicate protection. However, it is lightweight and efficient, making it well suited for applications that send small, frequent updates to multiple participants.

Use Cases

• Multiplayer games
• Real-time status broadcasting
• Lightweight messaging protocols

Devicespec Format

Client Mode

N[x]:UDP://<HOST>[:PORT]/

Example:

N:UDP://192.168.1.8:2000/           Send datagrams to host on port 2000

Server (Listening) Mode

N[x]:UDP://:<PORT>/

Since UDP is connectionless, the source address of the last received packet is automatically used as the destination for any outgoing data.

Example:

N:UDP://:2000/                      Listen for UDP packets on port 2000

TCP vs. UDP

HTTP/HTTPS

HTTP (HyperText Transfer Protocol) and its secure variant HTTPS allow the N: device to interact with web servers. FujiNet supports the common HTTP methods: GET, POST, PUT, and DELETE.

When HTTPS is specified, FujiNet negotiates a TLS (formerly SSL) encrypted connection, allowing your retro computer to communicate with secure web services.

Use Cases

• Downloading files from web servers
• Interacting with REST APIs
• Accessing secure web services (HTTPS)

Devicespec Format

N[x]:<HTTP|HTTPS>://[username:password@]<HOST>[:PORT]/<PATH>[?query=value&...]

Examples:

N:HTTP://ATARI-APPS.IRATA.ONLINE/BURIEDBU.COM
N:HTTPS://API.EXAMPLE.COM/DATA?FORMAT=JSON
N:HTTP://user:pass@MYSERVER/PRIVATE/FILE.TXT

Supported Operations

Notes

• HTTPS connections incur a brief pause on open while FujiNet negotiates TLS encryption with the remote host.
• HTTP authentication is performed when credentials are included in the URL.
• Query string parameters are fully supported and passed through to the server.

FTP

FTP (File Transfer Protocol) enables the N: device to browse directories and transfer files on FTP servers. FujiNet handles the full FTP session lifecycle (login, transfer, logout) for each operation.

Use Cases

• Browsing public FTP archives
• Downloading software and files
• Uploading files to an FTP server

Devicespec Format

N[x]:FTP://[username:password@]<HOST>[:PORT]/<PATH>

Examples:

N:FTP://FTP.PIGWA.NET/stuff/collections/      Browse a directory
N:FTP://FTP.PIGWA.NET/welcome.msg              Download a file
N:FTP://user:pass@MYSERVER/uploads/data.txt    Authenticated access

Supported Operations

Notes

• If no credentials are provided, anonymous login is performed with the password fujinet@fujinet.online.
• EPSV (Extended Passive Mode) commands are used to establish the data port connection.
• A CWD command is issued to navigate to the desired path before any file transfer.
• Connections are not persistent – a full login/logout cycle occurs for each file operation, similar to how a web browser handles FTP.

TNFS

TNFS (Trivial Network File System) allows the N: device to access files on TNFS servers. Unlike the TNFS support for the D: device (which operates on disk images at the sector level), the N: device operates on individual files stored on the TNFS server.

Use Cases

• Accessing files on a home TNFS server
• Sharing files across a local network
• Storing and retrieving data on network file storage

Devicespec Format

N[x]:TNFS://<HOST>[:PORT]/<PATH>

Examples:

N:TNFS://HOMESERVER/GAMES/FROG.EXE         Access a specific file
N:TNFS://192.168.1.50/DATA/                 Access a directory
N:TNFS://MYSERVER:16385/FILES/DOC.TXT       Non-default port

Supported Operations

Notes

• The TNFS server is mounted, used, and then unmounted for each operation.
• The server is always mounted from the root directory (/).
• Anonymous login is always used – username and password are not currently supported.
• If a D: device already has the same TNFS server mounted, the N: device will share that mount, avoiding redundant mount/unmount cycles.

Directories vs. Files

For protocols that support file system operations (HTTP, FTP, TNFS), it is important to distinguish between directory paths and file paths:

The trailing slash tells FujiNet whether to treat the resource as a directory (for listing) or a file (for reading/writing).

Error Codes

When a protocol operation fails, FujiNet returns an error code. Common network-related errors include:

For a complete list, see the error codes reference.

Next Steps

• N: Device Overview – high-level introduction
• Tools and Utilities – NCD, NCOPY, and other command-line tools
• BASIC Programming Examples – using protocols from BASIC