A little serial testing utility (found it helpful for identifying character stripping)

example socat

# Run this first, then recv, then send
socat pty,link=/tmp/ttySEND pty,link=/tmp/ttyRECV

serialtester.py

#!/usr/bin/env python3

import argparse
import os
import serial
import time as t

if __name__ == "__main__":
    a = argparse.ArgumentParser()
    a.add_argument('action', choices=("send", "recv"))
    a.add_argument('--baud', type=int, default=9200)
    a.add_argument('--ack', default="\r")
    a.add_argument('--encoding', default="latin-1")
    a.add_argument('--range-start', type=int, default=0)
    a.add_argument('--range-end', type=int, default=256)
    args = a.parse_args()

    s = serial.Serial(
        port="/tmp/tty{}".format(args.action.upper()),
        baudrate=args.baud,
        bytesize=serial.EIGHTBITS,
        parity=serial.PARITY_NONE,
        stopbits=serial.STOPBITS_ONE,
        rtscts=True,
        dsrdtr=True,
    )

    os.unlink("{}.out".format(args.action))

    if args.action == "send":
        for value in range(args.range_start, args.range_end):
            print("Sending {}".format(value))
            s.write(chr(value).encode(args.encoding))
            ch = s.read(len(args.ack))
            with open("send.out", "a") as sd:
                sd.write("{:3d}\t{}\n".format(value, chr(value).encode(args.encoding)))
            if ch == args.ack.encode():
                print("Ack'd")
    elif args.action == "recv":
        i = 0
        while True:
            data = s.read(1)
            print("Received {}".format(i))
            with open("recv.out", "a") as rd:
                rd.write("{:3d}\t{}\n".format(i, data))
            s.write(args.ack.encode(args.encoding))
            i += 1

    print("Finished")