TCP va uning ishonchliligi

class Tomon:
    def __init__(self, nom, boshlangich_seq):
        self.nom = nom
        self.holat = "YOPIQ"
        self.seq = boshlangich_seq
        self.kutilayotgan = None

    def holat_qoy(self, yangi):
        print(f"  {self.nom:<7} {self.holat} -> {yangi}")
        self.holat = yangi


mijoz = Tomon("mijoz", 1000)
server = Tomon("server", 5000)

print("1-qadam: mijoz SYN yuboradi")
mijoz.holat_qoy("SYN-YUBORILDI")
server.holat_qoy("TINGLAMOQDA")
print(f"  SYN seq={mijoz.seq}")
server.kutilayotgan = mijoz.seq + 1

print("2-qadam: server SYN-ACK bilan javob beradi")
server.holat_qoy("SYN-QABUL")
print(f"  SYN-ACK seq={server.seq} ack={server.kutilayotgan}")
mijoz.kutilayotgan = server.seq + 1

print("3-qadam: mijoz ACK yuboradi")
mijoz.seq += 1
mijoz.holat_qoy("ULANGAN")
print(f"  ACK seq={mijoz.seq} ack={mijoz.kutilayotgan}")
server.seq += 1
server.holat_qoy("ULANGAN")

print()
print("ikkala tomon ham ULANGAN holatida:",
      mijoz.holat == server.holat == "ULANGAN")
print("mijoz keyingi bayt raqami :", mijoz.seq)
print("server keyingi bayt raqami:", server.seq)

import socket

PORT = 9400

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server.bind(("127.0.0.1", PORT))
server.listen(1)

mijoz = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mijoz.connect(("127.0.0.1", PORT))
ulanish, _ = server.accept()

# Uchta alohida sendall - UDP da bu uchta datagramma bo'lardi
mijoz.sendall(b"birinchi")
mijoz.sendall(b"ikkinchi")
mijoz.sendall(b"uchinchi")
mijoz.shutdown(socket.SHUT_WR)

# Endi to'rt baytlik bo'laklarda o'qiymiz
print("to'rt baytlab o'qiymiz:")
bolaklar = []
while True:
    bolak = ulanish.recv(4)
    if not bolak:
        break
    bolaklar.append(bolak)
    print("  ", bolak)

print()
print("o'qishlar soni:", len(bolaklar))
print("birlashtirilgani:", b"".join(bolaklar).decode())
print("xabar chegarasi saqlandimi:", b"birinchi" in bolaklar)

mijoz.close()
ulanish.close()
server.close()

import socket
import struct

PORT = 9401


def xabar_yubor(s, matn):
    """Oldiga 4 baytlik uzunlik qo'yib yuboradi."""
    yuk = matn.encode()
    s.sendall(struct.pack("!I", len(yuk)) + yuk)


def aniq_oqi(s, nechta):
    """Kerakli baytlar to'liq kelguncha o'qiydi."""
    bufer = b""
    while len(bufer) < nechta:
        bolak = s.recv(nechta - len(bufer))
        if not bolak:
            raise ConnectionError("ulanish uzildi")
        bufer += bolak
    return bufer


def xabar_oqi(s):
    uzunlik = struct.unpack("!I", aniq_oqi(s, 4))[0]
    return aniq_oqi(s, uzunlik).decode()


server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server.bind(("127.0.0.1", PORT))
server.listen(1)

mijoz = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mijoz.connect(("127.0.0.1", PORT))
ulanish, _ = server.accept()

for matn in ["birinchi", "ikkinchi", "uchinchi xabar uzunroq"]:
    xabar_yubor(mijoz, matn)

for i in range(3):
    print(f"{i + 1}-xabar: {xabar_oqi(ulanish)}")

mijoz.close()
ulanish.close()
server.close()

XABAR = "Salom Husanboy"
BOLAK = 4

# Jo'natuvchi har baytga raqam beradi
paketlar = []
raqam = 1
for i in range(0, len(XABAR), BOLAK):
    bolak = XABAR[i:i + BOLAK]
    paketlar.append({"seq": raqam, "matn": bolak})
    raqam += len(bolak)

print("jo'natiladigan paketlar:")
for p in paketlar:
    print(f"  seq={p['seq']:<3} [{p['matn']}]")

# Ikkinchi paket yo'lda yo'qoladi
YOQOLGAN = 2
print()
print(f"--- {YOQOLGAN}-paket yo'lda yo'qoldi")

qabul = {}
kutilayotgan = 1
for n, p in enumerate(paketlar, 1):
    if n == YOQOLGAN:
        continue
    qabul[p["seq"]] = p["matn"]
    # Qabul qiluvchi HAR DOIM "keyingi kutilayotgan bayt" ni aytadi
    while kutilayotgan in qabul:
        kutilayotgan += len(qabul[kutilayotgan])
    print(f"  seq={p['seq']:<3} keldi -> ACK {kutilayotgan}")

print()
print("takroriy ACK soni jo'natuvchiga yo'qolishni bildiradi")
print("jo'natuvchi seq =", kutilayotgan, "dan qayta yuboradi")

# Qayta yuborish
p = paketlar[YOQOLGAN - 1]
qabul[p["seq"]] = p["matn"]
while kutilayotgan in qabul:
    kutilayotgan += len(qabul[kutilayotgan])
print(f"  seq={p['seq']:<3} qayta keldi -> ACK {kutilayotgan}")

tiklangan = "".join(qabul[k] for k in sorted(qabul))
print()
print("tiklangan xabar:", tiklangan)
print("asl bilan bir xilmi:", tiklangan == XABAR)