FB_SocketAccept

The remote client connection requests arriving at the TwinCAT TCP/IP Connection Server have to be acknowledged (accepted). The function block FB_SocketAccept accepts the incoming remote client connection requests, opens a new remote client socket and returns the associated connection handle. The connection handle is required by the function blocks FB_SocketSend and FB_SocketReceive in order to exchange data with the remote client, for example. All incoming connection requests first have to be accepted. If a connection is no longer required or undesirable, it can be closed with the function block FB_SocketClose.

A server implementation requires at least one instance of this function block. This instance has to be called cyclically (polling) from a PLC task. The block can be activated cyclically via a rising edge at the bExecute input (e.g. every 5 seconds).

If successful, the bAccepted output is set, and the connection handle to the new remote client is returned at the hSocket output. No error is returned if there are no new remote client connection requests. Several remote clients can establish a connection with the server at the same time. The connection handles of several remote clients can be retrieved sequentially via several function block calls. Each connection handle for a remote client can only be retrieved once. It is recommended to keep the connection handles in a list (array). New connections are added to the list, and closed connections must be removed from the list.

VAR_INPUT
    sSrvNetId       : T_AmsNetId := '';    
    hListener       : T_HSOCKET;      
    bExecute        : BOOL;         
    tTimeout        : TIME := T#5s;     
END_VAR

VAR_OUTPUT
    bAccepted   : BOOL; 
    bBusy       : BOOL;
    bError      : BOOL;
    nErrId      : UDINT;
    hSocket     : T_HSOCKET;
END_VAR