Compare Serial Port Splitters: Features, Performance, and Price

Serial Port Splitter: Top 5 Hardware and Software OptionsA serial port splitter lets you connect multiple devices to a single RS-232/RS-485/TTL serial interface. This can be useful in industrial automation, laboratory setups, legacy systems, or hobbyist projects where you need to monitor, log, or control several serial devices but only have one host serial port. Below I present five top hardware and software options, including pros, cons, and use-case recommendations to help you choose the right splitter for your setup.

Overview: when you need a serial port splitter

A serial port splitter can address several common needs:

• Connect multiple serial peripherals (sensors, PLCs, modems) to one PC or embedded host.
• Share a single device (e.g., modem) between multiple hosts.
• Monitor serial traffic from multiple devices concurrently.
• Convert between serial standards (RS-232 ↔ RS-485, TTL) while providing multiple endpoints.

Choose a hardware splitter when you need reliable electrical isolation, proper signal buffering, or support for different voltage levels. Choose software splitters when you need quick, flexible virtual ports on a PC without extra hardware.

Key selection criteria

Consider these technical aspects before choosing:

• Serial standard compatibility: RS-232, RS-422, RS-485, TTL.
• Number of channels/ports required.
• Directionality: one-to-many vs. many-to-one vs. many-to-many.
• Electrical isolation and surge protection.
• Data rates supported (baud rate).
• Flow control support (RTS/CTS, DTR/DSR, XON/XOFF).
• Operating system and driver support.
• Latency and buffering behavior.
• Power requirements and mounting (DIN-rail for industrial).
• Budget and warranty/support.

Top 5 Options

1) Hardware: B+B SmartWorx (formerly B&B Electronics) 485SD9TB or similar RS-485 splitters/isolators

• Summary: Industrial-grade RS-485 repeaters/isolators that let one master talk to multiple remote nodes or provide buffering and isolation between segments.
• Best for: Industrial automation, long-distance bus segments, noisy electrical environments.
• Pros: Robust electrical isolation, high reliability, wide temperature ranges, DIN-rail mounting, surge protection.
• Cons: Typically supports RS-485/RS-422 only (not RS-232), more expensive than simple converters.
• Use case example: Extending an RS-485 fieldbus across multiple floors while preserving signal integrity and preventing ground loops.

2) Hardware: MOXA NPort serial device servers (e.g., NPort 5100A series) with virtual COM port splitting

• Summary: Ethernet-to-serial device servers that expose serial devices over TCP/IP and allow multiple clients to connect simultaneously (depending on model and configuration).
• Best for: Remote access to serial devices, integrating serial gear into networked systems.
• Pros: Flexible network access, can serve multiple clients, support for RS-232/422/485 models, strong industrial specs.
• Cons: Requires network infrastructure; some models limit concurrent connections or require licensing for virtual COM features.
• Use case example: Multiple operators need access to a remote PLC’s serial console via the corporate LAN.

3) Hardware: Serial port hubs/splitters (true hardware RS-232 splitters)

• Summary: Passive or active RS-232 splitters that duplicate TX/RX lines to multiple DB9 connectors. Active models buffer signals to maintain signal levels across multiple devices.
• Best for: Simple setups where one host needs to connect to several RS-232 peripherals or for monitoring traffic.
• Pros: Simple, plug-and-play; active versions keep signal integrity; inexpensive options available.
• Cons: RS-232 is point-to-point by design — splitting can cause contention (two devices driving TX simultaneously) and flow-control issues; no protocol-level arbitration.
• Use case example: Feeding the same GPS serial output to a data-logger and a display simultaneously (where only one device transmits).

4) Software: Eltima Serial to Ethernet Connector / Virtual Serial Port Driver

• Summary: Windows and macOS software that creates virtual COM ports and redirects serial data over TCP/IP, or splits a local COM port into multiple virtual ports for different applications.
• Best for: Desktop applications needing multiple virtual ports, developers testing serial applications, or sharing a serial device between programs.
• Pros: Creates multiple virtual COM ports, flexible configuration, supports network redirection, easy to install.
• Cons: Software layer adds latency; licensing cost for commercial use; depends on host OS stability.
• Use case example: Running two different logging applications on the same PC that both need access to a GPS receiver’s serial stream.

5) Software/Open-source: com0com + com2tcp / socat (Linux) combo

• Summary: com0com is an open-source Windows virtual serial port driver that creates paired virtual COM ports; combined with com2tcp or socat, you can redirect or split serial streams over network or locally.
• Best for: Developers, hobbyists, and Linux/Windows power users who prefer free, scriptable tools.
• Pros: Free and highly configurable; powerful for testing and automation; socat supports many protocols.
• Cons: Steeper learning curve; less polished UI; requires manual configuration for splitting and multiplexing.
• Use case example: Creating a local virtual COM port pair where one end is connected to a terminal program and the other forwards data to multiple logging scripts.

Practical guidance — choosing between hardware and software

• Choose hardware if you need: electrical isolation, industrial reliability, true multi-drop buses like RS-485, or long cable runs.
• Choose software if you need: flexible virtual ports, quick sharing between applications, remote access without added hardware, or lower cost for desktop use.
• Hybrid approach: Use an Ethernet serial device server (MOXA) plus virtual COM software for broad compatibility and remote multi-client access.

Quick comparison

Implementation tips & gotchas

• Beware of contention: on RS-232, only one device should drive TX at a time—splitting can break this rule.
• Flow control: hardware splitters may not forward hardware flow-control signals correctly; test RTS/CTS behavior.
• Baud rate and timing: buffering/splitting can add latency—measure end-to-end if timing-critical.
• Grounding and isolation: in industrial environments, use isolated repeaters to avoid ground loops.
• Protocol-level solutions: when possible, use a master–slave protocol design (Modbus RTU, etc.) over RS-485 to avoid collisions.
• Software licensing: check virtual COM software licenses for commercial deployment.

Example setups

• Small lab: USB-to-RS232 adapter → active RS-232 splitter → data logger + serial console.
• Industrial floor: PLC (RS-485) → B+B SmartWorx isolator/repeater → multiple segment branches → MOXA device servers to bring branches onto Ethernet.
• Developer PC: GPS via USB → Eltima Virtual Serial Port creates two COM ports → logging app + mapping app access same data.

Conclusion

Pick a hardware splitter for reliability, isolation, and correct electrical behavior in industrial or noisy environments. Pick software splitters for desktop flexibility, quick sharing between programs, and remote access. For many real-world needs, a hybrid (device server + virtual COM software) offers the best balance of robustness and convenience.