No. Ethernet ports can't transmit or receive RS-232 signals.
If your laptop has a traditional DB9 RS-232 serial port, use that with the appropriate serial cable. If it doesn't, use a USB to RS-232 serial adapter.
Answer from Spiff on Stack ExchangeNo. Ethernet ports can't transmit or receive RS-232 signals.
If your laptop has a traditional DB9 RS-232 serial port, use that with the appropriate serial cable. If it doesn't, use a USB to RS-232 serial adapter.
If you have something like this item, then it is merely a pinout adapter and not a serial/ethernet device.
You could use one of these on each end of a RJ45 cable to make a serial cable. That serial cable could run through structured cable installed inside a wall or similar, but it cannot run through an ethernet switch or vlan.
How to: USB RS232 to RJ45 interface pinout | Hardware Canucks
Can I put RJ45 connectors on RS232 9-pin cable?
programming - Serial Communication with rs232/485 and rj45 - Electrical Engineering Stack Exchange
Serial Console over RJ45 Ethernet-Patchpanels / RS232-Ethernet-Pinout?
Videos
I have Belden 9539 (RS232 cable, 9 pin) already run in a building. Can I put an RJ45 connector on both ends of this cable, will it work? I'd just leave out the ground pin. I don't see why it wouldn't work, even if it's not the ideal solution. Any thoughts? This is for connecting the LAN port of a PTZ camera to the PTZ controller.
That RJ45 to USB cable is not an Ethernet adapter.
It might superficially look like one, but it’s not.
That cable you purchased is a known as console cable (aka: Cisco cable or rollover cable). It’s meant/designed to connect your PC to a server (or other enterprise level device) via RS232; aka serial connection or link. That is not an Ethernet adapter, and cannot be used as one at all.
Generally, what you are looking for is a USB to Ethernet adapter that looks something like this:
You would plug the USB side into your PC and then connect the Ethernet end to your LAN via an Ethernet cable. These are fairly common to come by and should be pretty affordable. Just make sure to check if the USB A to RJ45 adapter you purchase explicitly states it’s an Ethernet adapter.
The 8P8C connector (commonly known as RJ45, even though this is incorrect) is used for a lot of different things.
While nowadays its most common use is for (some kinds of) Ethernet, it can also be used:
- For RS-232 or other similar serial ports (instead of the more common DB-25 or DE-9 connectors), especially for console access on Cisco routers and other devices;
- For analogue telephony (aka POTS);
- For digital telephony (aka ISDN);
- For proprietary telephony systems;
- Sometimes even USB;
- And many other things.
The adapter you bought is for the first type: to connect to an RS-232 serial port presented as 8P8C (RJ45). It is completely unrelated to Ethernet.
What you need is a USB Ethernet adapter. They come in many different shapes and sizes, and have varying characteristics and performances (100 Mbit/s, Gigabit, 2.5GbE, USB 2, USB 3, USB-A, USB-C...). You need to make sure the description of the product includes "Ethernet", along with the specs you want.
Some docks (especially USB-C docks) also include Ethernet ports, so it may be an alternative if you need other interfaces (more USB, HDMI, etc.).
If your computer has a USB-C port, you're probably better off using an adapter using that kind of port. Given the low prices of such adapters, picking a 2.5GbE adapter is probably a good idea even if you won't use it at its maximum potential if your switch/router doesn't support such speeds.
While there are a few adapters that take the form of a cable (with a male "RJ45" at the other end like the one you bought), most will have a female connector, and you will then need an Ethernet cable to connect that to the corresponding connector on your switch or router. The advantage is that you can easily change the cable if you need shorter or longer distances (or if the cable or plug gets damaged).
Those plugs are most likely (hard to tell from a picture) Cisco console cable plugs.
They convert a DB-9 serial interface to a RJ45 receptacle , but NOT for use with a regular network cable. (They also exist in a DB-25 version.)
They are intended to use with a Cisco console cable (that has a RJ45 plug on 1 end and a DB-9 on the other) or a roll-over cable (RJ45 plug on both ends, but different pin-out than a network cable).
A Cisco console cable + a plug like yours connected to the other end make together a serial 3-wire null-modem cable.
A roll-over cable with 2 of these plugs (on each end) also makes a 3-wire null-modem cable.
That may be all you need. Provided that your lab-device needs a 3-wire null-modem cable, which is the most common case.
But some require a straight cable and in some (rare) cases you need a 5-wire null-modem (or straight) cable.
As modern computers, especially laptops, typically don't have a DB-9 serial port anymore, you may also need a USB to serial converter plug.
For short: There are a lot of variables here. Without more details about the devices involved and the exact nature of your plugs I can't get any more specific.
As Tonny wrote, that adapter is most likely a Cisco RJ45-to-DB9 converter, which is a purely passive adapter. The RJ45 side is not Ethernet, it's just RS232 on a different type of connector (Cisco devices used to have console ports with an RJ45 connector rather than the more common DB9 or DB25 connectors).
If you have an RS232 port on your laptop, then you just need a cable. While this was extremely common a couple of decades ago, nowadays I believe it's quite rare to find a laptop with an RS232 port.
So what you need instead is more likely an RS232-to-USB (aka serial-to-USB) converter/adapter.
Once you have that, you should have a new character device for the serial port somewhere in /dev (details may vary, but probably some kind of /dev/tty-something).
If you just want to capture the data from the serial port to a file, you can just cat /dev/serial_port_device_name >filename.
If you need to change serial port settings you can use stty but beware that you must keep the port open while you do it, otherwise the settings will reverse to defaults right away.
If you want something more foolproof, you can probably write a short script using the language of your choice, or they may be additional tools to manage that.
Alternatively there are devices with serial ports and Ethernet connections (you would then usually use telnet or netcat to connect to the serial ports and capture the data), but these would be more expensive, and only useful if you need to capture data from a larger distance.