6-2
Section
Using Socket Services with Socket Service Request Switches
97
Local UDP/TCP Port No.
Specify the number of the UDP or TCP port for the socket to use for communica-
tions.
•
Do not specify the port being used as the FINS UDP port (default: 9600) in an
open request for a UDP socket.
•
Do not specify FTP server TCP port numbers 20 and 21 in an open request for
a TCP port.
•
Do not specify mail communications TCP port number 25.
•
As a rule, use port numbers 1,024 and higher.
If port number 0 is specified when for an active TCP open, the TCP port number
will be automatically allocated and the number of the port that was opened will be
stored in the local UDP/TCP port number in the Socket Service Parameter Area
(i.e., the actual port number will be overwritten on the value of 0 set by the user).
Remote IP Address
Specify the IP address of the remote device.
•
This parameter is not used when making a receive request for a UDP socket.
The remote IP address will be stored with the response data and will be written
as the Remote IP Address in the Socket Service Parameter Area.
•
When opening a passive TCP socket, the combination of the remote IP ad-
dress and the remote TCP port number can be used to affect processing as
shown in the following table.
Remote IP
Address
Remote TCP
Port No.
Processing
0
0
All connection requests accepted.
0
Not 0
Connection requests accepted only for the
same port number.
Not 0
0
Connection requests accepted only for the
same IP address.
Not 0
Not 0
Connection requests accepted only for the
same port number and IP address.
If the Remote IP Address is set to 0, a connection can be made to any remote
node and the remote IP address of the node that is connected will be stored as
the Remote IP Address in the Socket Service Parameter Area. If a specific re-
mote I/O address is set, then a connection can be made only to the node with the
specified address.
If the Remote TCP Port No. is set to 0, a connection can be made to any remote
node regardless of the TCP port number it is using. If a specific remote TCP port
number is set, then a connection can be made only to a node using the specified
TCP port number.
Remote UDP/TCP Port No.
Specify the UDP or TCP port number used by the remote device.
•
This parameter is not used when making a receive request for a UDP socket.
The remote UDP/TCP port number will be stored with the response data and
will be written as the Remote UDP/TCP Port No. in the Socket Service Param-
eter Area.
•
When opening a passive TCP socket, the combination of the remote IP ad-
dress and the remote TCP port number can be used to affect processing as
shown in the table for the Remote IP Address, above. If the Remote UDP/TCP
Port No. is set to 0, the UDP/TCP port number of the remote device will be writ-
ten as the Remote UDP/TCP Port No. in the Socket Service Parameter Area.
