Design and Development of a Diagnostics Client for a Beam Loss ...

Design and Development of a Diagnostics Client for a Beam Loss Measurement System at CERN
ables requested channels of the BLEDP module. The detailed logic of how the embedded
BLEDP server transmits data from the input channels can be found on [10].
4.3 Client Server Architecture Protocol
A specific architecture was discussed, designed and then implemented for the communi-
cation of the Java client and the embedded server inside the FPGA. As already mentioned,
the server application is limited to serve only one client at a time and when other requests
come they are refused. The connection is established via a standard TCP/IP handshake
between the two applications, after a connection request from the client is received by the
server. The first thing sent by the server is the MAC address of the module on which it
is running. This MAC address is used by the client in the logging protocol specified. The
top folder which contains data from a specific module is named after this address. This
logging-to binary files protocol will be discussed later on. The next thing done by the client
is to send a command to the server in order to specify several parameters like the amount
of expected data, the data format and the channel number it would like to receive. In re-
sponse to that command, the server will either start the data transmission or it will stop
all active transmissions. The corresponding options concerning readout and triggering for
this command are listed in the following chapter.
4.3.1 Commands Sent by the Client
There are three groups of commands sent by the client to the server. All types use a
TCP socket for communication. The first group is called Acquisition commands and re-
fer to an online acquisition. After the establishment of a connection with the server, a
start command is sent. It contains all the critical information for the acquisition, like the
mode, channel number and time. On the other hand, a stop command can be sent at any
time, before the end of a requested acquisition time. This command is triggered by the
stop button in the graphical interface. The server simply terminates the data flow after
receiving this command and the client reinitializes. The last acquisition command con-
tains the destination UDP port in the server. The UDP stream sent by the server will be
addressed to that port. This command is sent only if multi-channel mode is selected. The
user is responsible to open this port, so that incoming UDP data won’t be blocked by a
firewall or other computer protection. The second group of commands is called Expert
or Static commands. The purpose of these commands is to set the values of different
internal registers of the BLEDP hardware, such as relays and potentiometers. The third
group is called Advanced or Dynamic commands. Its purpose is to add a dynamic set of
commands to control different hardware elements in the card. All the commands sent by
the client share a common characteristic. Every command has a fixed size of 7 bytes. The
first two bytes constitute the header, which the server uses to distinguish them. Further-
more, the next 4 bytes represent the payload of the command. This payload has different
meaning depending on the type. The last byte is a CRC byte and is used to protect against
Emmanouil I. Angelogiannopoulos 24