VISA or GPIB might possibly be accessible directly by way of TCP, but true serial ports would not be, and neither would serial over USB: for those you would need to have a process on the server that talked to the port.
However, on some operating systems, it is possible to share devices over a networked file system. If you are using one of those operating systems, then you would not yourself access the remote device via TCP: that layer would be handled on your behalf. Instead you would locate the remote device in your system's name space and open it. For example, there is a possibility that you could use something like
s = serial('YourServerName:/dev/ttyd3')
or
s = serial('YourServername::COM3')
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