selenium打开浏览器底层实现原理中的异常4(Failed to establish a new connection: [WinError 10061] 由于目标计算机积 极拒绝，无法连接)

代码：

#coding=utf-8

import requests

import json

url='http://127.0.0.1:4444/wd/hub/session'

data = json.dumps({

    'desiredCapabilities':{

        'browserName':'MicrosoftEdge'

    }

})

print(requests.post(url,data).json())

结果：

PS E:\30.Study\30.自动化测试\99.零基础入门 Python Web 自动化测试\10.seleniumCodePractice> & "C:/Program Files/Python38/python.exe" "e:/30.Study/30.自动化测试/99.零基础入门 Python Web 自动化测试/10.seleniumCodePractice/202006/requests_open_browser.py"
Traceback (most recent call last):
  File "C:\Program Files\Python38\lib\site-packages\urllib3\connection.py", line 156, in _new_conn
    conn = connection.create_connection(
  File "C:\Program Files\Python38\lib\site-packages\urllib3\util\connection.py", line 84, in create_connection
    raise err
  File "C:\Program Files\Python38\lib\site-packages\urllib3\util\connection.py", line 74, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [WinError 10061] 由于目标计算机积极拒绝，无法连接。

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Program Files\Python38\lib\site-packages\urllib3\connectionpool.py", line 665, in urlopen
    httplib_response = self._make_request(
  File "C:\Program Files\Python38\lib\site-packages\urllib3\connectionpool.py", line 387, in _make_request    
    conn.request(method, url, **httplib_request_kw)
  File "C:\Program Files\Python38\lib\http\client.py", line 1230, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "C:\Program Files\Python38\lib\http\client.py", line 1276, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "C:\Program Files\Python38\lib\http\client.py", line 1225, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "C:\Program Files\Python38\lib\http\client.py", line 1004, in _send_output
    self.send(msg)
  File "C:\Program Files\Python38\lib\http\client.py", line 944, in send
    self.connect()
  File "C:\Program Files\Python38\lib\site-packages\urllib3\connection.py", line 184, in connect
    conn = self._new_conn()
  File "C:\Program Files\Python38\lib\site-packages\urllib3\connection.py", line 168, in _new_conn
    raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x000001D22D03D490>: Failed to establish a new connection: [WinError 10061] 由于目标计算机积
极拒绝，无法连接。

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Program Files\Python38\lib\site-packages\requests\adapters.py", line 439, in send
    resp = conn.urlopen(
  File "C:\Program Files\Python38\lib\site-packages\urllib3\connectionpool.py", line 719, in urlopen
    retries = retries.increment(
  File "C:\Program Files\Python38\lib\site-packages\urllib3\util\retry.py", line 436, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='127.0.0.1', port=4444): Max retries exceeded with url: /wd/hub/session (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x000001D22D03D490>: Failed to establish a new connection: [WinError 10061] 由于目标计算机积极拒绝，无法连接。'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "e:/30.Study/30.自动化测试/99.零基础入门 Python Web 自动化测试/10.seleniumCodePractice/202006/requests_open_browser.py", line 10, in <module>
    print(requests.post(url,data).json())
  File "C:\Program Files\Python38\lib\site-packages\requests\api.py", line 119, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "C:\Program Files\Python38\lib\site-packages\requests\api.py", line 61, in request
    return session.request(method=method, url=url, **kwargs)
  File "C:\Program Files\Python38\lib\site-packages\requests\sessions.py", line 530, in request
    resp = self.send(prep, **send_kwargs)
  File "C:\Program Files\Python38\lib\site-packages\requests\sessions.py", line 643, in send
    r = adapter.send(request, **kwargs)
  File "C:\Program Files\Python38\lib\site-packages\requests\adapters.py", line 516, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='127.0.0.1', port=4444): Max retries exceeded with url: /wd/hub/session (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x000001D22D03D490>: Failed to establish a new connection: [WinError 10061] 由于目标计算机积极拒绝，无法连接。'))
PS E:\30.Study\30.自动化测试\99.零基础入门 Python Web 自动化测试\10.seleniumCodePractice>

原因分析：

【requests.exceptions.ConnectionError: HTTPConnectionPool(host='127.0.0.1', port=4444)】可知，是连接http失败。即下图中selenium服务没有启动，导致无法连接。

 对应方法：

找到"selenium-server-standalone-3.141.59.jar"所在路径，通过"java -jar selenium-server-standalone-3.141.59.jar"启动selenium即可。

验证是否启动成功，通过在浏览器地址栏里输入“http://127.0.0.1:4444/”来验证，成功的话，下图会表示出来：