You can set up virtual serial ports connections for vSphere virtual machines in several ways. The connection method that you select depends on the task that you need to accomplish.

You can set up virtual serial ports to send data in the following ways.

Physical serial port on the host

Sets the virtual machine to use a physical serial port on the host computer. This method is useful for using an external modem or a hand-held device in a virtual machine.

Output to file

Sends output from the virtual serial port to a file on the host computer. This method is useful for capturing the data that a program running in the virtual machine sends to the virtual serial port.

Connect to a named pipe

Sets a direct connection between two virtual machines or a connection between a virtual machine and an application on the host computer. With this method, two virtual machines or a virtual machine and a process on the host can communicate as if they were physical machines connected by a serial cable. For example, you can use this option for remote debugging on a virtual machine.

Connect over the network

Enables a serial connection to and from a virtual machine's serial port over the network. The Virtual Serial Port Concentrator (vSPC) aggregates traffic from multiple serial ports onto one management console. vSPC behavior is similar to physical serial port concentrators. Using a vSPC also allows network connections to a virtual machine's serial ports to migrate seamlessly when you use vMotion to migrate the virtual machine. For requirements and steps to configure the Avocent ACS v6000 virtual serial port concentrator, see

You can select a client or server connection for serial ports. Your selection determines whether the system waits for a connection or initiates it. Typically, to control a virtual machine over a serial port, you select a server connection. This selection allows you to control the connections, which is useful if you connect to the virtual machine only occasionally. To use a serial port for logging, select a client connection. This selection allows the virtual machine to connect to the logging server when the virtual machine starts and to disconnect when it stops.

Before you connect network-backed virtual serial ports, you must add one of the following firewall rule sets to prevent the firewall from blocking traffic:

VM serial port connected to vSPC. Use to connect the serial port output through a network with the Use virtual serial port concentrator option enabled to allow only outgoing communication from the host.

VM serial port connected over network. Use to connect the serial port output through a network without the virtual serial port concentrator.


Do not change the allowed IP list for either rule set. Updates to the IP list can affect other network services that might be blocked by the firewall.

For details about adding rule sets to a firewall, see the vSphere Security documentation.

When you use a physical serial port for serial port passthrough from an ESXi host to a virtual machine, the following conditions apply:


Not Supported

Serial ports that are integrated into the motherboard

Migration with vMotion


Serial ports connected through USB are not supported for serial port passthrough. They might be supported by USB passthrough from an ESXi host to a virtual machine. See USB Configuration from an ESXi Host to a Virtual Machine.