Page 142 - Welding Robots Technology, System Issues, and Applications

Robotic Welding: System Issues 129

CASE “system_state”:
system_state; SocketSend client_socket1 \Str := answer_string;
CASE “variable_read”:
variable_read(par_1, par_2); SocketSend client_socket1 \Str :=
answer_string;
CASE “variable_write”:
variable_write(par_1, par_2, par_3); SocketSend client_socket1
\Str := answer_string;
CASE “io_read”:
io_read(par_1, par_2); SocketSend client_socket1 \Str :=
answer_string;
CASE “io_write”:
io_read(par_1, par_2, par_3); SocketSend client_socket1 \Str :=
answer_string;
DEFAULT:
SocketSend client_socket1 \Str := -9999;
ENDTEST
SocketClose client_socket1;
ELSE Ignore connections if server
WaitTime 0.1; is disabled
SocketClose client_socket1;
ENDIF
ENDWHILE
ERROR Retry socket listen if
SocketClose client_socket1; socket timed out
retry_sock:=1;
TRYNEXT;
UNDO
SocketClose server_socket;
SocketClose client_socket1;
ENDPROC
ENDMODULE
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Figure 4.12. TCP/IP socket server RAPID code [43][44]

This server was placed on the controller running as an extra-task, i.e., the robot has
a main task, where the foreground applications are running, and a second task used
to communicate with the external computer: to receive commands and exchange
information.

Third step – write the client program: any TCP/IP socket server should be
capable of receiving and accepting connections from client applications, receive
and process commands, and deliver the obtained results. The following example
(Figure 4.13) is a simple TCP/IP socket client program coded using the Microsoft
Visual Basic .NET 2003 developing suite.