Establish client/server communications

Identify the process for starting and ending communication between IBM i Access Client Solutions clients and host servers.

This topic also includes each server's port numbers, and a description of server daemons and their role in communication.

Client/Server communication is established in the following steps:

  1. To initiate a server job that uses sockets communications support, the client system connects to a particular server's port number.
  2. A server daemon must be started (with the STRHOSTSVR command) to listen for and accept the client's connection request. Upon accepting the connection request, the server daemon issues an internal request to attach the client's connection to a server job.
  3. This server job may be a prestarted job or, if prestart jobs are not used, a batch job that is submitted when the client connection request is processed. The server job handles any further communications with the client. The initial data exchange includes a request that identifies authentication tokens that are associated with the client user. A user profile and password, or a Kerberos ticket, are examples of these tokens.
  4. Once the authentication tokens are validated, the server job switches to use the IBM i user profile associated with those tokens, and changes the job by using many of the attributes defined for the user profile, such as accounting code and output queue.

Server to client communications

IBM i Access Client Solutions uses TCP/IP to communicate with the system servers. The optimized servers use IBM i sockets support to communicate with clients. The IBM i sockets support is compatible with Berkeley Software Distributions 4.3 sockets over TCP/IP. Sockets support is provided with the 5770-TC1 product that is installed on the system.

Start of changeUsing the host connection server to establish connectionsEnd of change

Start of changeThe host connection server (HCS) can be used to authenticate once and transfer new connections to other host servers without needing to reauthenticate. Connect to the HCS as described above to establish an authenticated connection. Once the authenticated connection is established, the client can transfer new connections to other host servers without reauthenticating with the following steps:
  1. The client connects to HCS using the HCS port.
  2. The HCS daemon listens for and accepts the client’s connection. The connection is transferred to an HCS job.
  3. The client sends a series of requests over both the authenticated connection and the new connection. The new connection is then attached to a server job and the job switches to use the IBM i user profile and other attributes of the user profile for the authenticated connection.
End of change

See the TCP/IP Configuration and Reference manual for more information about communications.

For more information, see: