400PLC与上位机通讯只需要配置好CP1613通过监控软件就可以直接读取和控制PLC了，你为什么还要用FC50呢？
Meaning of the Block

The AG_RECV/AG_LRECV function (FC) receives the data transferred on a configured connection from the Ethernet CP.
The data area specified for data acceptance can be a process image area, a memory bit area or a data block area.
Error-free execution is indicated when the data could be received from the Ethernet CP.
Note:
Remember the following when using TCP connections:
With the S7 CPs for the S7-400, you must use FC AG_LRECV on TCP connections!