The best replacement for udp is tcp.

The best alternatives to udp are rated as following:
★★★★★  tcp
★★  ip
★★  rtp
★★  tcp ip
★★  http
★  tcp openvpn
★  tcp port
★  tcp speed
★  tcp ports
★  icmp
★  tcp vpn
★  tcp faster
★  ftp
★  tcp minecraft
★  ssyn
★  tcp/ip
★  tcp performance
  tcp protocol
  multicast
  websocket
  tcp wiki
  tcp sip
  ipsec over tcp
  idp
  rmi
  tcp nfs
  rtsp
  tcp\/ip
  sctp
  udp
  raw ip

Your alternative for udp is not listed? Suggest!
Speaking about udp, one probably shouldn't forget about tcp.

Other search terms related to udp and their ratings are:
★★★★★ tcp
★★★★★ ping
★★★ rtp
You have in mind a companion for udp and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of udp in all years. Click on graph for more.
udp
tcp
ip