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Port 80 Proxying

Overview

Centova Cast includes a port-80 proxy that can be enabled on the Settings page of the Centova Cast administration area. This enables listeners to tune in to audio streams using TCP port 80 (the port normally used for serving web pages) which may be useful for listeners who are behind restrictive firewalls that prevent access to the port numbers normally used by streaming servers.

When enabled, a link will be displayed on the stream start page (also available in the client's control panel in the "Tune-in" section in the lower right-hand corner) allowing the listener to optionally tune in through the proxy.

Technical Considerations

Be advised that there are serious technical considerations when using any port-80 proxy implementation that works through a web server. Because of the way Apache works, every listener connected to a stream you host will require one dedicated Apache server process for the entire time they are connected and listening to the stream. The exact memory consumption of each Apache process can be determined on a Linux server by running "ps aux" and checking the "RSS" column for an httpd process. Typical memory consumption is somewhere between 10MB - 25MB per process, as a fairly conservative estimate.

The result of this limitation is that every listener connected to a stream hosted on your server will use 10-25MB of your server's memory, in addition to the memory used by ShoutCast. Even if the server is not very busy, this will result in a significant allocation of memory -- with 20 simultaneous listeners, for example, the server would use 200 - 500MB of memory just for proxying. With 100 simultaneous listeners, that figure would rise to 1GB - 2.5GB, which would cause many servers to run out of memory.

While this issue is not advertised by most companies, this limitation is not specific to Centova Cast, and is true of all web-based ShoutCast/IceCast proxy scripts. Proxying through Apache is supported by Centova Cast only because of significant client demand, and Centova Technologies does not recommend their use.