Manage virtual serial lines on the Internet

[Sergio Bertana]

Using converters ethernet-serial it is possible to virtualize serial lines using an Internet connection. For example, it is possible to connect in serial with a device located in a geographic position distant from ours using an Internet connection.

The devices can be configured as a server or as a client, when the server and the client are connected via a TCP / IP network, be it a local ethernet and / or a VPN and / or the Internet, the data received from the serial port of a device are retransmitted output from the other device, simulating the operation of a serial cable.

A client device connects to the server device whose IP address is set in its configuration. If the server is not reachable, it retries the connection until the connection can be established. It is therefore evident that if the devices are connected to the Internet via MODEM connected to PSTN or GSM telephone lines, ISDN or ADSL lines, as soon as the connection to the network is established, the two devices connect, virtualizing the serial line.

Remember that the PC can also be used as a master or slave device, requiring in this case the use of only one converter device.

[Massimo]

Description of the various ways to connect to an ethernet-serial converter such as the TRP-C31. Conditions:

2 LAN both connected to the Internet: the LAN (A) made up of n Ethernet-connected PCs where one of them acts as a router to the Internet (ADSL); the LAN (B) made up of a PC and a TRP-C31 connected in ethernet and in which the PC acts as a router to the internet (PSTN).

Purpose: From a PC on the LAN (A) you want to “see” the serial line of the TRP-C31 on the LAN (B) obviously through the internet.

Result: There are 3 ways to "see" the serial line of the TRP-C31:
1) With a TCP client running on a LAN PC (A) that connects to the TCP server running on the TRP-C31
2) Using VirtualCOM in a LAN PC (A) that connects to the TCP server in run on the TRP-C31
3) Using an additional TRP-C31 connected in ethernet to the LAN (A) and set in client operation that connects to the TCP server in run on the TRP-C31

Note: For the test, the connection to the internet by the LAN router (B) gives the PC a dynamic IP. So to connect from the LAN (A) you need to know it. In reality, to make things easier, it would be necessary to have a static IP.

1 mode) Just run the appropriate PAT-NAT on the LAN router PC (B) in order to direct the connection to the TCP server on the TRP-C31. From a PC on the LAN (A) using a TCP client program (eg: Remoter) with an IP equal to the IP with which the PC router on the LAN (B) connected to the internet, you "see" the serial of the TRP on LAN (B) (tried!).

2 mode) Install VirtualCOM on the LAN PC (A) and associate the virtual COM to the IP address with which the LAN PC router (B) connected to the internet. Run the appropriate PAT-NAT on the LAN router PC (B) in order to direct the connection to the TCP server on the TRP-C31. Add a second PAT-NAT to redirect the TCP 5300 port (also used by VirtualCOM).

3 mode) Just run the appropriate PAT-NAT on the LAN router PC (B) in order to direct the connection to the TCP server on the TRP-C31. The TRP on the LAN (A), by setting the IP address with which the PC router of the LAN (B) has connected to the internet, when switched on it connects to the TRP server on the LAN (B). From a PC on the LAN (A) connected with a serial cable to the TRP, I “see” the serial of the TRP on LAN (B) (tried!).

Notes for VirtualCOM:
To install it, you do it after installing the “TRP-C3x Manager” program. Just go to Start-Programs-Trycom and launch “Install VirtualCOM”. Follow the directions proposed.

The installation of VirtualCOM expects to have a TRP-31 connected to the LAN. Then install VirtualCOM with the TRP connected to the local network and then connect the TRP in the remote network. After installation, the VirtualCOM parameters can be changed from the “TRP-C3x Manager” program by setting the IP with which the LAN PC router (B) is connected to the internet.

In VirtualCOM, it is also possible to change the baudrate of the serial port of the LAN TRP (B). In fact, for example, the baudrate change that Remoter implements during the upload of a program works (tried!).

[Author]

Post