I don't want to be presumptive about you or your application, but we see this question monthly here. It is always, ALWAYS, easier, faster, more reliable, and cheaper to use one of the pre-developed communication drivers to communicate between a PLC and a PC or server. Use OPC-DA, OPC-UA, Modbus/TCP, the PLCIO or RTA libraries... anything but "open a socket and send a string".
But to answer your direct question, the Socket object programming reference is RA Publication ENET-AT002.