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Sockets

The socket node-type is the most comprehensive and complex one. It allows to send and receive simulation data over the network. Internally it uses the well known BSD socket API.

Please note that only datagram / packet, connection-less based network protocols are supported. This means that there's currently no support for TCP!

The implementation supports multiple protocols / OSI layers:

  • Data-Link Layer 2: Raw Ethernet Frames (no routing!)
  • Network Layer 3: Raw IP (internet / VPN routing possible)
  • Transport Layer 4: UDP encapsulation, TCP client or server

Prerequisites​

This node-type does not have any special library dependencies. It is always available.

Optionally, libnl3 is used to setup network emulation as described in page Netem Emulation.

Implementation​

The source code of the node-type is available here: https://github.com/VILLASframework/node/blob/master/lib/nodes/socket.cpp

Configuration​

For TCP connection, the node can only be either server or client which is specified by "tcp-server" or "tcp-client" in the layer section.

Format Object (object) or Format Name (string) (format_spec)
layer
string
Default: "udp"
Enum: "udp" "ip" "eth" "tcp-client" "tcp-server"

Select the network layer which should be used for the socket. Please note that eth can only be used locally in a LAN as it contains no routing information for the internet.

verify_source
boolean
Default: false

Check if source address of incoming packets matches the remote address.

object (Input configuration (received by VILLASnode))
object (Output configuration (sent out by VILLASnode))
vectorize
integer
Default: 1

This setting allows to send multiple samples in a single message to the destination nodes.

The value of this setting determines how many samples will be combined into one packet.

Array of Hook Object (object) or Hook Name (string) (hook_list)
builtin
boolean (Builtin hook functions)
Default: true

By default, each node and paths has a couple of default hooks attached to them. With this setting the attachment of built-in hooks can be disabled.

{
  • "format": "villas.human",
  • "layer": "udp",
  • "verify_source": false,
  • "in": {
    },
  • "out": {
    },
  • "vectorize": 1,
  • "hooks": [
    ],
  • "builtin": true
}

Example​

node/etc/examples/nodes/socket.conf
nodes = {
    udp_node = {
        type = "socket"

        # Receive and sent 30 samples per message (combining)
        vectorize = 30

        # The maximum number of samples this node can receive
        samplelen = 10

        # By default, all nodes will have a few builtin hooks attached to them
        # When collecting statistics or measurements these are undesired
        builtin = false

        # Layer can be one of:
        #   - udp   Send / receive L4 UDP packets
        #   - ip    Send / receive L3 IP packets
        #   - eth   Send / receive L2 Ethernet frames (IEEE802.3)
        layer = "udp"


        format = "gtnet"

        in = {
            # This node only received messages on this IP:Port pair
            address = "127.0.0.1:12001"

            # Check if source address of incoming packets matches the remote address
            verify_source = true
        }

        out = {
            # This node sends outgoing messages to this IP:Port pair
            address = "127.0.0.1:12000"
        }
    }

    # Raw Ethernet frames
    ethernet_node = {
        type = "socket"

        layer = "eth"

        in = {
            address = "12:34:56:78:90:AB%lo:12002"
        }

        out = {
            address = "12:34:56:78:90:AB%lo:12002"
        }
    }

    # Datagram UNIX domain sockets require two endpoints
    unix_domain_node = {
        type = "socket"
        layer = "unix"

        in = {
            address = "/var/run/villas-node/node.sock"
        }

        out = {
            address = "/var/run/villas-node/client.sock"
        }
    }

    udp_multicast_node = {
        type = "socket"

        in = {
            # This node only received messages on this IP:Port pair
            address = "127.0.0.1:12001"

            # IGMP multicast is only support for layer = (ip|udp)
            multicast = {
                enabled = true

                # The multicast group. Must be within 224.0.0.0/4
                group = "224.1.2.3"

                # The IP address of the interface which should receive multicast packets
                interface = "1.2.3.4"

                # The time to live for outgoing multicast packets
                ttl = 128

                # Whether or not to loopback outgoing multicast packets to the local host
                loop = false
            }
        }

        out = {
            # This node sends outgoing messages to this IP:Port pair
            address = "127.0.0.1:12000"
        }
    }
}