Emulate network latency in Linux

increase_network_latency.sh

# Install iproute (Ubuntu)
sudo apt-get install iproute

# Increase network latency in eth0 (250 milliseconds)
sudo tc qdisc add dev eth0 root netem delay 250ms

# Delete network modifications
sudo tc qdisc del dev eth0 root netem

# To make this change in localhost you must only replace "eth0" to "lo" ( --- WARNING --- in this case time will double )
sudo tc qdisc add dev lo root netem delay 250ms

More info: https://tuongvy7.wordpress.com/2017/04/07/linux-network-packet-loss-emulation-with-netem-ubuntu/