BOINC client–server technology refers to the model under which BOINC works. The BOINC framework consists of two layers which operate under the client–server architecture. Once the BOINC software is installed in a machine, the server starts sending tasks to the client. The operations are performed client-side and the results are uploaded to the server-side.

Design and structure of BOINC

Server structure

A major part of the BOINC system is the backend server. The server can run on one or many machines to allow BOINC to scale easily to projects of any size. BOINC servers run on Linux-based computers and use Apache, PHP, and MySQL for their web and database systems. Scientific computations run on participants' computers. After uploading from the user's client to a science investigator's database, the backend server validates and analyzes the results. The validation process involves running all tasks on multiple contributor PCs and comparing the results. BOINC servers also provide these features: The server consists of two CGI programs and (normally) five daemons, written in C++. Computations to be performed by clients are called workunits. A result describes an instance of a workunit, even if it hasn't been completed. A project does not explicitly create results; the server creates them automatically from workunits. The scheduler CGI program handles requests from clients, receiving completed results and sending new work to compute. The scheduler doesn't get available results directly from the database. Instead, a feeder daemon loads tasks from the database and keeps them in a shared-memory block, which the scheduler reads. The feeder periodically fills empty "slots" in the shared-memory block after the scheduler has sent those results to a client. When all the results from a workunit are completed and returned, the validator checks them. One popular method would be to compare the results against each other. The validator can have custom project-code to do fuzzy comparison between results, or it can perform a bitwise comparison. If the validator determines that at least some of the results are valid, it marks the work unit and the valid results as valid, users who returned legitimate results are granted credit for it, and a "canonical result" is chosen. If the results don't agree, or if one of the results is not reported by its deadline, the server generates an additional instance of the job, and sends it to a third host. This is repeated until a quorum of matching results is found or a limit on the number of instances is reached. Next, the assimilator daemon processes the canonical result using project-specific code. For example, some projects may parse the file and store information in a database, others may just copy the file somewhere else. An assimilator may also generate more workunits based on the returned data. The file_deleter daemon deletes output files after the assimilator has processed them, and deletes input files that aren't needed anymore. The transitioner daemon handles state transitions of workunits and results. It also generates results from workunits when they are first created, and when more are needed (for example, if a result turns out invalid).

Client structure

BOINC on the client is structured into a number of separate applications. These intercommunicate using the BOINC remote procedure call (RPC) mechanism. These component applications are: Since BOINC has features that can render it invisible to the typical user, there is risk that unauthorized and difficult to detect installations may occur. This would aid the accumulation of BOINC-credit points by hobbyists who are competing with others for status within the BOINC-credit subculture.

Client platforms