code: function receive(intf, srcIP, destIP, u8, headerOffset) {
    const srcPort = udpHeader.getSrcPort(u8, headerOffset);
    const destPort = udpHeader.getDestPort(u8, headerOffset);
    const dataLength = udpHeader.getDataLength(u8, headerOffset) - udpHeader.headerLength;
    const dataOffset = headerOffset + udpHeader.headerLength;
    debug('recv UDP over IP4', srcPort, destPort, dataLength);
  
    const socket = UDPSocket.lookupReceive(destPort);
    if (!socket) {
      return;
    }
  
    const u8data = u8.subarray(dataOffset);
    if (socket.onmessage) setImmediate(() => socket.onmessage(srcIP, srcPort, u8data));
  }
docs: const portUtils = require('./port-utils'); const IP4Address = require('./ip4-address'); const interfaces = require('./interfaces'); const netError = require('./net-error');