As a network server, the fundamental operation of scream is to acquire serial data from instruments, and transmit blocks in UDP packets on a network. The list of clients that will be sent data is shown in the ‘Clients’ table at the top of the page. Client types (push/pull) can be mixed for the same Scream server. To differentiate, the timeout parameter can be used – ‘push’ clients have no timeout, pull clients have a timeout that is refreshed by the client. If the timeout expires, the client is removed from the list.
Actual block-by-block details of transmitted data are indicated in the lower left pane - ‘Block Tx’.
Other server operations will be logged by messages in the ‘Control’ pane (lower right).
To enable any data transmission, the ‘Transmit data from local Com Ports’ option should be checked. This applies to both push and pull type data transfer.
To limit the data rate sent on the network, a lower sample rate ceiling can be specified using the ‘X sps transmitted block limit’ Default value is 200 (effectively all data). An example of usage for this feature is if a digitiser is configured to generate 4sps and 100sps continuous data, and the 100sps data should be recorded locally, but the 4sps should also be transmitted on a low bandwidth network for remote monitoring purposes.
Setting this value to zero would suppress all data, but still transmit status information.
Scream can act as a conduit from a network connection to a device connected to a local serial port. Use ‘Allow remote access to Com Ports’ to control this access. If you wish to change the configuration of the equipment remotely, you should enable this option. If you are concerned about security, and potential problems from outside interference, disable this option.
You can add client to push data to by right-clicking in the ‘Clients’ list box, and selecting the ‘Add’ option. Type in the IP address and port number of the destination, separated by a colon (:). To setup a broadcast, use the IP address 255.255.255.255. To send data to another process on the same computer, use the IP address 127.0.0.1. To restrict broadcasts to a particular subnet, use ‘255’ as a wildcard: for example 192.168.255.255:1567 will broadcast data on port 1567 to clients on the 192.168 subnet only.
Note that several destinations or broadcasts can be added, and data will be sent to each one simultaneously.
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