UDP datagrams
UDP is a connectionless transport protocol. There is no handshake: a sender simply sends a datagram to an address and port. Each datagram is delivered, if it is delivered at all, as one whole unit, so message boundaries are preserved, unlike TCP's byte stream.
Python
import socket
receiver = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
receiver.bind(("127.0.0.1", 0))
address = receiver.getsockname()
sender = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sender.sendto(b"one", address)
sender.sendto(b"two", address)
first, _ = receiver.recvfrom(1024)
second, _ = receiver.recvfrom(1024)
sender.close()
receiver.close()
print(first, second)