Port 650 is the official home of OBEX (OBject EXchange)—the protocol that enables wireless file transfers between devices over Bluetooth, infrared, and other transports.
What OBEX Does
OBEX is a session protocol for exchanging binary objects between devices. It handles the transfer of files, contacts (vCards), calendar entries, and other data objects. The protocol operates as a simple client-server system: one device requests or sends objects, the other responds.1
Despite the name sounding technical, you use OBEX every time you:
- Send a photo from your phone to someone via Bluetooth
- Receive a contact card wirelessly
- Transfer files between devices without cables
The protocol is deliberately simple—designed to work over any reliable transport without complex negotiations. It borrows design concepts from HTTP, using a request-response model that feels familiar to anyone who's built web applications.2
The History: From Infrared to Bluetooth
OBEX was born in the infrared era. The Infrared Data Association (IrDA) released version 1.0 in January 1997 to enable devices to exchange data over line-of-sight IR links.3 The goal was simple: two devices in close proximity should be able to share small objects—business cards, files, calendar entries—without cables or complex setup.
The Palm III, introduced in 1998, popularized this capability with its "beaming" feature. Users would point their Palm Pilots at each other, tap a button, and watch data transfer via infrared. OBEX powered those transfers, and "beaming" became a verb.4
But OBEX's real longevity came from its transport-agnostic design. When Bluetooth emerged as the dominant short-range wireless standard, the Bluetooth Special Interest Group adopted OBEX in 1999 as a foundational protocol. The Object Push Profile (OPP), released with Bluetooth 1.0 in July 1999, used OBEX to enable file transfers over radio instead of infrared.5
OBEX survived the death of consumer infrared technology because it wasn't tied to infrared. The same protocol now runs over Bluetooth, USB, RS-232, TCP/IP networks, and even in specialized devices like Livescribe smartpens.6
How OBEX Works
OBEX operates as a client-server protocol with straightforward operations:
CONNECT — Client initiates a session with the server
PUT — Client sends a file or object to the server
GET — Client requests a file or folder listing from the server
SETPATH — Client navigates to a different folder
DISCONNECT — Client closes the session
The client issues a request and waits for the server's response before sending another request. Each operation can include headers describing the object being transferred—its name, type, size, modification time.7
When you send a photo over Bluetooth, your phone (acting as OBEX client) opens a connection to the recipient's phone (acting as OBEX server), sends a PUT command with the photo's metadata and data, and waits for confirmation. The simplicity is the point—no complex handshakes, no elaborate state machines.
Port 650 and Network OBEX
While OBEX is most commonly used over Bluetooth (where port numbers don't apply in the traditional sense), port 650 is the official TCP port for OBEX when it runs over IP networks.8
This allows OBEX to work over:
- Local networks where devices want to exchange files without Bluetooth pairing
- Internet connections for remote object exchange (less common)
- Development and testing environments
On Linux systems, OBEX server implementations like obexpushd bind to port 650 by default when listening for network connections. This requires root privileges since 650 falls in the well-known port range (0-1023).9
Security Considerations
OBEX was designed for convenience in an era when wireless file transfer was novel. Security was not the primary concern.
No built-in encryption — The base OBEX protocol doesn't encrypt transfers. When running over Bluetooth, you get whatever security the Bluetooth pairing provides. Over TCP, the connection is cleartext unless wrapped in TLS.
Authentication is optional — OBEX supports authentication, but it's not required. Many implementations accept connections without verifying the sender's identity.
File overwrites — OBEX PUT operations can overwrite existing files if the server allows it. Malicious or accidental overwrites are possible.
If you're running an OBEX server on port 650 over a network, firewall it carefully. Only allow connections from trusted devices. Consider whether you actually need network OBEX—most modern use cases work fine over Bluetooth where pairing provides a basic security boundary.
Related Protocols and Ports
Port 5900 — VNC (Virtual Network Computing) for screen sharing
Port 9100 — Raw print protocol
Port 3689 — DAAP (Digital Audio Access Protocol) for music sharing
These protocols share OBEX's philosophy: simple object or service access without complex authentication.
Why OBEX Matters
OBEX is nearly 30 years old and still works. Your modern Android or iOS device likely supports it, quietly handling Bluetooth file transfers using a protocol designed when Palm Pilots ruled the PDA world.
It survived because it was simple, transport-agnostic, and solved a real problem. Files needed to move between devices. OBEX made that happen without requiring users to understand protocols, ports, or network stacks. Point, click, accept—done.
Port 650 is rarely seen in the wild because Bluetooth doesn't expose traditional port numbers to users. But when OBEX runs over TCP—in development environments, specialized embedded systems, or network-based object exchange—this is where it lives.
The protocol that made "beaming" a verb is still here, quietly moving files between devices, outliving the infrared technology that created it.
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