Thank you!
I was able to get a barcode printed out with the help of @pturmel and @JordanCClark !
I changed my foundService if statement to this:
if foundService:
print('Found serv')
strMessage100 = '^XA'
strMessage112 = '^FO50,50^B3N,N,100,Y,N^FD%s^FS' % serialNum
strMessage113 = '^XZ'
strOut = strMessage100+strMessage112+strMessage113
Which prints out the barcode alongside the serial number. Though when I go to scan this barcode it seems that the serial number isn't within the barcode itself.
Scratch that, it seems to be printing the serial number within the barcode! 
Full working code for solution:
def printLabel(serialNum, printerName):
from javax.print import PrintService, PrintServiceLookup, DocFlavor, SimpleDoc
from java.lang import System
from org.python.core.util import StringUtil
from java.net import Socket
from java.io import DataOutputStream
foundService = False
printServices = PrintServiceLookup.lookupPrintServices(None, None)
for printService in printServices:
print("Made it in loop")
if printerName in printService.toString():
foundService = True
# break
if foundService:
print('Found serv')
strMessage100 = '^XA'
strMessage112 = '^FO50,50^B3N,N,100,Y,N^FD%s^FS' % serialNum
strMessage113 = '^XZ'
strOut = strMessage100+strMessage112+strMessage113
job = printService.createPrintJob()
flavor = DocFlavor.BYTE_ARRAY.AUTOSENSE
byteArray = StringUtil.toBytes(strOut)
doc = SimpleDoc(byteArray, flavor, None)
job.print(doc, None)