Ethernet Port and Network Communications
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Just like any other Ethernet device, the DS has a unique MAC-address (defined by the MAC-address (FE) setting) and must be assigned a valid IP-address (defined by the IP-address (IP) setting) to function properly on the network. Unique MAC-address is preset during the production. Assigning a valid IP-address is the responsibility of the user. IP-address can be assigned manually or automatically, through DHCP (must be enabled through the DHCP (DH) setting).
To route the data between attached serial device and the network host the DS needs to establish and maintain a data connection. Depending on current Transport Protocol [setting/ parameter] the data connections can use TCP/IP or UDP/IP.
The DS only allows for a single data connection. This is because the serial port is not a shared media and cannot be controlled by more than a single network source at any given time. This is analogous to the COM port of the PC, which can only be opened by one program at a time.
The DS is capable of both accepting incoming connections (passive opens) and establishing outgoing connections of its own (active opens). Whether passive and/or active opens are allowed is defined by the current Routing Mode (RM) [setting/ parameter].
Passive opens, when allowed, are accepted from any network host as long as correct transport protocol is used (must match current Transport Protocol [setting/ parameter]) and connection is made to a correct data port (defined by the Data Port (DP) setting). [V3.24/3.54+]: Current Source IP Filtering [setting/parameter] defines whether an incoming connection will be accepted from any network host or only the host whose IP-address matches the one specified by current Destination IP-address (DI) [setting/parameter/instruction].
When performing an active open the DS attempts to connect to the current Destination IP-address (DI) [setting/parameter/instruction] and current Destination Data Port (DP) [setting/parameter/instruction]. When the destination is located on a different subnet, which is derived from comparing the destination IP-address, IP-address of the DS itself, and the netmask (defined by the Netmask (NM) setting), the DS connects through default gateway or [V3.54+] PPPoE Access Concentrator:
Exactly when the DS attempts to establish an outgoing connection (when such connections are allowed) depends on the selected connection mode (see Connection Mode (CM) setting). Attached serial device can optionally control and monitor connection establishment and termination through a dedicated set of instructions known as modem commands (serial-side parameters and instructions), or through the DSR line manipulation (when enabled through the Connection Mode (CM) setting) and DTR line monitoring (see DTR mode (DT) setting). Data connections can also be closed automatically, on timeout (see Connection Timeout (CT) setting).
In addition to "normal" data connections the DS supports data connections through the Link Server.
Besides the user-definable data port there are also two identical UDP command ports with numbers 65535 (FFFF Hex) and 32767 (8FFF Hex). Network programming of the DS is effected by sending programming commands (as UDP datagrams) to either port. Additionally, programming commands can be sent (under certain conditions) right within the data connection itself- see inband (TCP) commands and command-phase (TCP) commands.
Programming of the DS and data routing can be performed concurrently, these processes are completely independent from each other.
The DS also supports ARP and ICMP protocols- it can be PINGed just like any other network device.