Transports

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In Ice terminology, a transport is a conduit for exchanging Ice protocol messages. Ice supports a number of transports; some of them are built into the Ice core, while others are available as plug-ins. Your transport selection will be driven by application requirements. For example, the TCP transport might be acceptable for deployment on a trusted intranet, while an Internet-facing application will generally use SSL or WSS (WebSocket Secure).

Most transports have a configuration component, which is often done statically via the application's external configuration file. Some transports also provide an API for accessing special features programmatically. Finally, certain Ice features might not be available with all transports. For example, you can send oneway invocations with any transport, whereas twoway invocations require a stream-oriented transport and datagram invocations require the UDP transport.

You'll need to choose a transport as soon as you're ready to test your first client-server prototype, if not sooner. The server's object adapter and the client's proxy must have at least one matching endpoint, where an endpoint is simply a transport name together with any necessary options. Ice uses a simple text-based syntax for configuring endpoints.

All of Ice's IP-based transports support both IPv4 and IPv6, as long as the underlying platform also supports both. Both are enabled by default; you can disable one of them with the Ice.IPv4 or Ice.IPv6 property, and make Ice try the IPv6 addresses of a host name first with Ice.PreferIPv6Address. These properties are not available in JavaScript.

The following table summarizes the transports that Ice provides and indicates whether they are built into the Ice core in C++, C#, Java, and indirectly in the C++-based implementations:

TransportCore?Connection Oriented?IP-based?Description
tcp, ssl
Yes
Yes
Yes
tcp is the default transport in Ice; ssl is tcp with TLS, using your platform's native SSL implementation.
udp
Yes
No
Yes
Supports unicast and multicast datagram invocations.
ws, wss
Yes
Yes
Yes
WebSocket and secure WebSocket, especially useful when a client needs to communicate with a back-end service from a web browser application.
bt, bts
No
Yes
No
Bluetooth, available on Linux and Android.
iap, iaps
Yes, on iOS.
Yes
No
Communicates with accessories over Bluetooth or the Lightning connector; C++ applications install it explicitly.

Ice for JavaScript supports a different set of transports:

TransportSupported in Browser?Supported with Node.js?Notes
tcp
No
Yes
Ice for JavaScript can only create outgoing connections.
udp
No
No
ssl
No
No
ws
Yes
Yes (Node.js >= 24)
wss
Yes
Yes (Node.js >= 24)