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.
Can I put RJ45 connectors on RS232 9-pin cable?
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Serial Console over RJ45 Ethernet-Patchpanels / RS232-Ethernet-Pinout?
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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.
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.
It's not clear exactly what you want. If you want to use your existing Ethernet port, that won't be an option for many reasons; the most fundamental being that Ethernet requires precise termination and voltage levels, the hardware on the interface (the PHY) is made to deal with that. Ethernet uses strictly +/- 0.85V and 50ohm termination impedance; RS-232 uses at a minimum +/- 3V, and could be as high as +/-25V, typically +/-12V. I imagine if you did try to connect your Ethernet port to an RS-232 line, it would fry your network interface.
Socat is a whole other level, and definitely is not useful here: it's a TCP/IP communication tool: it doesn't know anything about the electrical characteristics of the underlying hardware - it could talk over an RS232 line, but it'll be talking TCP, and you'd need to talk TCP on the other side for it to work.
Now, if what you're doing is designing a board, you could put an RJ45 jack with traces to a serial I/O port, which is exactly what the makers of your PCIX board have done. I've also seen Cisco routers like this.
The tool you really need is an RS232->USB converter.
Many devices use nonstandard connectors for serial ports. RJ-45 is probably the most common connector used for RS-232 serial after DB-9, but unlike with DB-9, there aren't even de facto standards for the pinout. I'm aware of 4 different RJ-45 RS-232 pinouts, and there are probably others I haven't seen yet.
None of this means that people are somehow converting Ethernet to serial. They merely happen to use the same connector.
There are many products that do provide that conversion, and in fact most of them do use the RJ-45 connector for their serial side. For an example of a single-port converter, there's the Digi One SP. More common are boxes that provide multiple serial ports, like the Digi PortServer and the Avocent (neรฉ Cyclades) Console Servers. These are just two examples out of many. Digi and Avocent are easily the two biggest players, but there are lots of smaller companies doing things like this.
Some of these boxes present themselves to the OS as /dev/ttyWHATEVER by installing a driver. These have the advantage that any program that knows how to talk to a serial port can talk to the remote device plugged into the converter. For the most part, the driver makes the converter appear no different from a local serial port. For example, if a program opens one of the converter's /dev/ nodes and calls cfsetospeed() on it to set the serial port's bit rate, the driver forwards the command to the remote converter box, which changes the serial bit rate on that port.
The main problem you run into with that type of converter is that it isn't always possible to find a working driver for your particular kernel. This problem is becoming more common as the popularity of RS-232 drops, since it means the companies providing these boxes have dwindling incentives to keep enhancing their driver to track kernel differences.
The other major type of serial to Ethernet converter is purely a network appliance. For example, with the Cyclades boxes, if it gets the IP 10.1.2.3 from the DHCP server, you can connect to 10.1.2.3 on TCP port 7001 to connect to the first serial port. You'd use TCP port 7002 for the second serial port, and so forth.
To set serial port parameters with this sort of converter, you typically have to use a web management UI hosted by the converter box. While this does mean you don't get features like automatic serial port parameter forwarding to the converter, you do get compatibility with any program that can open a TCP connection without needing a driver.