Network Sockets

Socket Basics

XCS provides a built-in tether module, known as Socket for handling network communication. Socket is an XCSE-native tether module that provides low-level networking protocols, e.g. Ethernet Drivers, Internet Protocol (IP) Addresses.

Sockets are essentially a user interface for internet/networking within modules. Sockets allow your computer to talk to the local area network's router through Ports.

Socket provides these commands for accessing ports:

• open PORT PROTOCOL
• close PORT
• read PORT
• write PORT DATA

See sections below for example uses.

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UDP Sockets

XCS provides sockets for User Datagram Protocol (UDP) communication. UDP is very fast, but operates with roughly 30% data loss. It is best practice to use UDP sockets when several packets are sent in a short period, and each packet is not particularly important.

See the following code example, which opens a UDP socket on port 80:

  request socket_open 80 UDP

After the socket has been opened, any other function within the module can use the following commands to write/read data to/from the socket:

 request socket_write 80 data
 request socket_read  80

When a socket is no longer needed (or the module has concluded), the socket must be closed by the program. This can be done like so:

  request socket_close 80

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TCP/IP Sockets

XCS provides Transmission Control Protocol (TCP) sockets for high-reliability networked communication. Unlike UDP, TCP will detect if a packet does not go through correctly and will resend the packet. So every TCP packet that is sent will be received by the client otherwise they are resent.

Although resending the packet ensures the information is delivered, it has a profound impact on efficiency and security. Flooding TCP sockets is a popular Dedicated Denial-of-Service (DDoS) strategy, so developers must detect/route attacks. Infrastructural mitigation is planned but not yet developed.

To open a socket for TCP on port 80:

  request socket_open 80 TCP

Once the socket is opened, data can be written/read exactly as it is in the UDP example. See below:

 request socket_write 80 data
 request socket_read  80

As with any other type of socket, make sure to close it at the end, so the network manager knows it is inactive.

  request socket_close 80

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