OpenSound Control in Max/MSP for Macintosh and Windows

The OpenSound Control protocol and UDP communication have been implemented in Cycling 74's Max/MSP environment.

The most reliable implementation of the UDP part is the udpsend and udpreceive externals that are now distributed with Max 4.6. CNMAT recommends these over our own (or anybody else's) older implementations. (Why? 1. Because they interact cleanly with Max's threading and scheduling systems, 2. Because they were written recently rather than being a port of a port of a port..., and 3. because they're cross-platform.) If you have an older version of Max, you can download these objects for OSX or Windows.

The udpsend and udpreceive externals implement a limited subset of the OSC protocol, but they're compatible with CNMAT's OpenSoundControl and OSC-route objects, which are available from CNMAT's Max/MSP Downloads Page:

• OpenSoundControl: This object takes Max-style data (flat "lists" consisting of a "message" plus "arguments") and formats it into the OpenSound Control protocol. It also parses incoming OpenSound Control packets and outputs their contents as Max-style data.
• OSC-route: Like Max's built-in "route" object, but for URL-style slash-delimited addresses instead of just Max lists. Also implements OSC's pattern matching language.

We recommend downloading Peter Nyboer's OTUDP primer (zip or sit) for an example of Max to Max communication (though it refers to the obsolete OTUDP instead of udpsend/udpreceive) and information on how to configure networking settings on Mac OSX, Mac OS9, and Windows.

Older UDP Implementations for Max

CNMAT no longer recommends, uses, or supports any of the following Max externals:

• otudp: A UDP object for PPC using Apple's OpenTransport networking system, written by Matt Wright. (Download OTUDP 3.0.2 for OSX/CFM)
• udp: The old UDP object, written in Think C, and available only as a 68k external, written by Mike Lee and then maintained by Matt Wright. You must use this object if you're running on a 68k Mac or if you're using Max 3.0 or earlier or if you're not running Open Transport. You can also use this object with Max68K3.5 (or later). This object does not work with MaxFAT3.5 (or later) on PowerPC Macs. (Available at CNMAT's OS9 Max Downloads page.)
• udp-read and udp-write: UDP receiving/sending externals for Windows, written by Emmanuel Fléty at IRCAM and now hosted by Remy Muller. See the OpenSoundControl page of Remy Muller's blog at IRCAM for info about these.

UDP Versus OSC

UDP, the "User Datagram Protocol," is the Internet Protocol for sending packets (a.k.a. "datagrams") between machines without establishing a connection between the machines and without any expensive mechanism for detecting lost packets and retrying them. UDP is used for streaming video and audio and many other applications on the Internet.

Open Sound Control is an application-level protocol invented by CNMAT. OSC defines only the bit format and interpretation of those bits; you could transmit OpenSound Control messages via UDP, TCP, shared memory, compact disc, a serial port, or any other digital medium.

Because UDP can be used to transmit many kinds of data besides OSC, and because OSC can be transmitted by many kinds of networking technology besides UDP, CNMAT's implementations put the UDP part and the OSC part in separate objects. People have used the OTUDP object without the OpenSoundControl object to send and receive data in formats other than OSC. (This requires writing a max external to translate between Max data and binary data in the non-OSC format.) These uses of OTUDP would also work with udpsend/udpreceive (via the "FullPacket" message).Conversely, people have used OpenSoundControl without UDP as a sort of super pack/unpack, to be able to pass entire OSC bundles as single Max messages.