The server daemon is a batch job associated with a particular server type.
There is only one server daemon for each of the different server types (such as database, network print, and signon). Each server type has a one-to-many relationship between its server daemon and the actual server jobs; one server daemon potentially has many associated server jobs.
The server daemon allows client applications to start communications with a host server that is using sockets communications support. The server daemon does this by handling and routing incoming connection requests. Once the client establishes communications with the server job, there is no further association between the client and the server daemon for the duration of that server job.
Subsystems must be active to use server or file server jobs. When shipped, all server jobs are configured to run in the QUSRWRK subsystem, but you can change the subsystem in which they run. File server jobs and the database host server daemon job (QZDASRVSD) run in the QSERVER subsystem.
The Start Host Server command starts server daemon jobs. The server daemons must be active for client applications to establish a connection with a host server that is using sockets communications support.
If you are starting the database daemon or the file server daemon, the QSERVER subsystem must be active. If you start any of the other server daemons, the QSYSWRK subsystem must be active. To use the prestart jobs for the server daemons that run in the QSYSWRK subsystem, QUSRWRK must be active.
The server mapper daemon is a batch job that runs in the QSYSWRK subsystem. It provides a method for client applications to determine the port number associated with a particular server.
This job listens on a well-known port for a connection request from a client. The well-known port number for TCP/IP is 449. The client sends the service name to the server mapper. The server mapper obtains the port number for the specified service name from the service table. The server mapper returns this port number to the client, ends the connection, and returns to listen for another connection request. The client uses the port number returned from the server mapper daemon to connect to the specified server daemon.
The server mapper daemon starts with the STRHOSTSVR command and ends with the ENDHOSTSVR command.