ICA Browsing the Old-Fashioned WayUDP Port 1604
Two different ports can be used for ICA browsing. Which port is used depends both on how you set up your servers and how you set up your clients.
The old-fashioned method of ICA browsing always used UDP port 1604. This port can be used for ICA browsing on all versions of both MetaFrame and WinFrame. It is the only port choice available for ICA browsing with WinFrame and MetaFrame 1.8 without Feature Release 1. This port number cannot be changed in any version of WinFrame or MetaFrame. This is the port used when you choose TCP/IP as the protocol when configuring the server locations within the ICA client.
By default, in older versions of the ICA client, when you browsed for an ICA service your ICA browsing occurred over port UDP 1604. Instead of sending out a packet directed at a particular server, older versions of the ICA client sent out a broadcast packet on the network to all servers in search of the master browser or data collector for the farm. Although you could manually specify a server address on older versions of the ICA client, the default was to broadcast a packet out. This is what the (Auto) setting meant in the Server Location tab in versions of the 32-bit ICA client prior to 6.20Auto meant broadcast.
The problem with broadcasts is that every single device on a local network will receive and have to process the broadcast packet, even if it is not the type of device the broadcast was intended for. On large networks, broadcast packets can be a significant source of problems and can cause networkwide slowdowns.
Although MetaFrame 1.8 servers would always respond to UDP 1604 broadcasts, MetaFrame XP servers, by default, do not. The design changes in XP make it obvious that Citrix is beginning to discourage the use of broadcasts for ICA browsing. In fact, the use of UDP port 1604 is discouraged in general with MetaFrame XP. Even for administrators who are using MetaFrame 1.8, the use of UDP port 1604 for ICA browsing is no longer necessary so long as you have installed Feature Release 1 for MetaFrame 1.8. As you will see in the following sections, the new ports of choice for ICA browsing are ports 80 and 443.