Maximum cable length for 5V or 3.3V I2C, UART, or 1-wire signals over Ethernet and how to increase it?
For longer distances, and greater immunity to electrical noise, differential signalling is often used.

For example RS-422

RS-422 drivers are relatively low-cost (start at under £2). They can be connected directly to the UART for point-to-point communication.

There are also specific drivers to extend the range of I2C e.g. NXP datasheet or TI datasheet. 

These should work well over twisted pair cables, e.g. Ethernet twisted pairs.