Tutorial: Sockets - nim-lang/Nim GitHub Wiki

The first thing you need to do is import the sockets module
import sockets
Then you need to create and initialize a TSocket object
var s: TSocket = socket()
After that you can use s.connect("addr", TPort(80)) to connect to a server
Once you connect to a server, you can send and receive messages to/from the server by using s.send("Message") to send, and s.recv() to receive.

import sockets, strutils

when not defined(strutils.toStringSep):
    proc toStringSep(x: int64): string = 
        var s = $x
        result = ""
        var j = 0
        for i in countdown(len(s)-1, 0): 
            inc(j)
            if j == 4: 
                result = ',' & result 
                j = 0
            result = s[i] & result

proc toMiB(size: int64): int64 =
    return size div 1024 div 1024

proc formatSize(size: int64): string =
    var gigabytes: int64 = size div 1024 div 1024 div 1024
    var megabytes: int64 = size.toMiB()
    var kilobytes: int64 = size div 1024
    if gigabytes != 0:
        return toStringSep(gigabytes) & "GB"
    elif megabytes != 0:
        return toStringSep(megabytes) & "MB"
    elif kilobytes != 0:
        return toStringSep(kilobytes) & "KB"
    else:
        return toStringSep(size) & "B"

var s = socket()

s.connect("irc.freenode.net", TPort(6667))

s.send("NICK NimrodBot\c\L")
s.send("USER NimrodBot * 0 :IRC Bot programmed in Nimrod!\c\L")

while True:
  var data: string = ""
  discard s.recvLine(data)
  echo(data)
  if data.split()[0] == "PING":
    s.send("PONG " & data.split()[1] & "\c\L")
  if data.split()[1] == "001":
    s.send("JOIN #nimrod\c\L")
  if data.split()[1] == "PRIVMSG":
    if data.split()[3] == ":!about":
      var msg = "NimrodBot 0.1 compiled on " & CompileDate & " " & CompileTime
      msg.add(" running on " & hostOS)
      s.send("PRIVMSG " & data.split()[2] & " :" & msg & "\c\L")

    elif data.split()[3] == ":!mem":
      var msg = "Occupied memory: " & formatSize(int64(getOccupiedMem()))
      s.send("PRIVMSG " & data.split()[2] & " :" & msg & "\c\L")

    elif data.split()[3] == ":!freemem":
      var msg = "Free memory: " & formatSize(int64(getFreeMem()))
      s.send("PRIVMSG " & data.split()[2] & " :" & msg & "\c\L")

    elif data.split()[3] == ":!totalmem":
      var msg = "Total memory: " & formatSize(int64(getTotalMem()))
      s.send("PRIVMSG " & data.split()[2] & " :" & msg & "\c\L")