Serial and USB Device Servers

Which serial standard does your equipment speak?

Serial equipment uses one of three electrical standards, and the device server must support the one on your machine. RS-232 is the familiar short-cable, point-to-point link with a DB9 connector. RS-422 and RS-485 use balanced pairs that carry data over much longer runs, and RS-485 lets several devices share one bus. Many multi-standard servers let you select the mode per port. Count the ports you need, from single-port units up to 16-port models, then check the connector type and whether you need a straight or a null-modem cable.

Network modes, drivers and USB limits

On the Ethernet side a serial link barely needs more than 10/100, so the software matters more than raw speed. Look for a virtual COM port driver for your operating system, which lets old applications talk to the server as if the device were plugged in, and for raw TCP or UDP modes if you write your own software. USB device servers share a USB device across the network through vendor software, and not every device type works that way, so check the vendor's list of supported devices.

Questions about Serial and USB Device Servers

What is the difference between RS-232 and RS-485?

RS-232 links two devices over short cables using single-ended signals. RS-485 uses a differential pair, tolerates noise better, reaches much further and supports many devices on one bus. They are not wire-compatible, so match the server's port mode to your equipment, or choose a model that can switch between them.

What is a virtual COM port?

It is a driver that makes a remote serial port appear as a local COM port on your computer. Software written for a serial cable can then talk to the equipment over Ethernet without changes, as long as the driver supports your operating system version.

Can I use any USB device through a USB device server?

Not always. Printers, storage drives and dongles often work, but devices that stream audio or video in real time may not, and some equipment expects a direct cable connection. Check the vendor's compatibility list before relying on it for a critical device.