TCP 与 UDP 套接字延迟基准

Question

我在 Python 中实现了一个通过 TCP 和 UDP 进行套接字通信的小型基准测试。令人惊讶的是，TCP 的速度几乎是 UDP 的两倍。

为了避免路由影响，服务器和客户端运行在同一台 Unix 机器上，但在不同的线程上。

也许代码有用。这是服务器代码：

import socket
import sys

host = 'localhost'  
port = 8888
buffersize = 8
server_address = (host, port) 

def start_UDP_server():
    socket_UDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    socket_UDP.bind(server_address)

    print("UDP server is running...")

    while True:
        data, from_address = socket_UDP.recvfrom(buffersize)
        if not data: break
        socket_UDP.sendto(data, from_address)
    socket_UDP.close()


def start_TCP_server():
    socket_TCP = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    socket_TCP.bind(server_address)
    socket_TCP.listen(1)

    print("TCP server is running...")

    while True:    
        client, client_address = socket_TCP.accept()

        while True:
            data = client.recv(buffersize)
            if not data: break
            client.sendall(data)

        client.close()

因此您可以运行 start_TCP_server() 或 start_UDP_server()。

客户端代码为：

import socket
import sys
import time

host = 'localhost'  
port = 8888
buffersize = 8
server_address = (host, port) 
client_address = (host, port+1)
N = 1000000


def benchmark_UDP():
    socket_UDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
    socket_UDP.bind(client_address)

    print("Benchmark UDP...")

    duration = 0.0
    for i in range(0, N):
        b = bytes("a"*buffersize, "utf-8")
        start = time.time()
        socket_UDP.sendto(b, server_address)
        data, from_address = socket_UDP.recvfrom(buffersize)
        duration += time.time() - start

        if data != b:
            print("Error: Sent and received data are bot the same")

    print(duration*pow(10, 6)/N, "µs for UDP") 


def benchmark_TCP():
    socket_TCP = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    socket_TCP.connect(server_address)

    print("Benchmark TCP...")

    duration = 0.0
    for i in range(0, N):
        b = bytes("a"*buffersize, "utf-8")
        start = time.time()
        socket_TCP.sendall(b)
        data = socket_TCP.recv(buffersize)
        duration += time.time() - start

        if data != b:
            print("Error: Sent and received data are bot the same")

    print(duration*pow(10, 6)/N, "µs for TCP")
    socket_TCP.close()

与服务器一样，您可以通过 benchmark_TCP() 或 benchmark_UDP() 开始基准测试。

TCP 的结果约为 25 µs，Unix 上的 UDP 约为 54 µs，[=35= 更糟]（TCP 大约 30 µs，UDP 超过 200 µs）。为什么？我希望 UDP 的优势很小。

Answer 1

您的 TCP 套接字已连接，但 UDP 套接字未连接。这意味着对 UDP 套接字上的每个 send/receive 进行额外处理。在 each side 上为 UDP 套接字调用 connect，就像在 TCP 套接字上调用 connect/accept 一样。

类似 iperf 的程序会执行此操作以准确测量。

TCP 与 UDP 套接字延迟基准

TCP vs. UDP socket latency benchmark

python

sockets

udp

tcp