client1.nim

var data = file.readFile()
var filedata = splitToChunks(data,24)
echo filedata
for i in filedata:
    echo i
    client.send(i & "\r\L")
client.send("DONE" & "\r\L")

client2.nim

var data = file.readFile()
var filedata = splitToChunks(data,24)
echo filedata
for i in filedata:
    echo i
    client.send(i & "\r\L")
client.close()

server1.nim

var data = ""
var output = open("D:\\test.txt",fmWrite)
while data != "DONE":
  echo "Receving..."
  output.write(data & "\r\L")
  data = client.recvLine()
echo "DONE"

server2.nim

const MAX_BUFFER_SIZE = 1024
var buffer: array[MAX_BUFFER_SIZE, char] # pre-allcated buffer
var output = open("D:\\test.txt",fmWrite)
var readLength = server.recv(addr buffer, MAX_BUFFER_SIZE) # server try to read 104 bytes from client, but if client send less, it will return in readLength
while readLength != -1: # if there is no data, or client disconnected, readLength will returns -1
  echo "Receving..."
  output.writeBuffer(addr buffer, readLength) # write everything it read from client to output file
  readLength = server.recv(addr buffer, MAX_BUFFER_SIZE) # continue receiving
server.close()