#!/usr/bin/python3
# stalk client allowing specification of the TCP congestion algorithm

from socket import *
from sys import argv

default_host = "localhost"
portnum = 5431

cong_algorithm = 'vegas'

def talk():
    global cong_algorithm
    rhost = default_host
    if len(argv) > 1:
        rhost = argv[1]
    if len(argv) > 2:
        cong_algorithm = argv[2]
    print("Looking up address of " + rhost + "...", end="")
    try:
        dest = gethostbyname(rhost)
    except gaierror as mesg:    # host not found
        errno,errstr=mesg.args
        print("\n   ", errstr);
        return;
    print("got it: " + dest)
    addr=(dest, portnum)
    s = socket()

    TCP_CONGESTION = 13   # defined in /usr/include/netinet/tcp.h
    cong = bytes(cong_algorithm, 'ascii')
    try:
       s.setsockopt(IPPROTO_TCP, TCP_CONGESTION, cong)
    except OSError as mesg:
       errno, errstr = mesg.args
       print ('congestion mechanism {} not available: {}'.format(cong_algorithm, errstr))
       return

    res=s.connect_ex(addr)      # make the actual connection
    if res!=0:
        print("connect to port ", portnum, " failed")
        exit()

    while True:
        try:
            buf = input("> ")
        except:
            break;
        buf = buf + "\n"
        s.send(bytes(buf, 'ascii'))

talk()