端口的问题以及绑定端口(Python)

### 【python2】使用固定源端口发送http请求
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背景需求：相同五元组信息的TCP会话
代码：
```python
import requests
from requests.adapters import HTTPAdapter
from requests.adapters import DEFAULT_POOLBLOCK
from urllib3 import PoolManager

######################
#     python 2.x     #
######################

class SourcePortAdapter(HTTPAdapter):
    """Transport adapter" that allows us to set the source port."""

def __init__(self, port, *args, **kwargs):
        self.poolmanager = None
        self._source_port = port
        HTTPAdapter.__init__(self, *args, **kwargs)

def init_poolmanager(self, connections, maxsize, block=DEFAULT_POOLBLOCK, **pool_kwargs):
        self.poolmanager = PoolManager(
            num_pools=connections, maxsize=maxsize,
            block=block, source_address=('', self._source_port))

s = requests.Session()
url = "http://172.168.0.1:8080/index"
s.mount(url, SourcePortAdapter(10001))
web = s.get(url, headers={'Connection':'close'})  # Connection:close 解决Failed to establish a new connection 问题
# web.encoding = 'utf-8'
print(web.status_code)   #查看返回码
print(web.text)          #查看网页内容
s.close()

```
参考来源：https://stackoverflow.com/questions/47202790/python-requests-how-to-specify-port-for-outgoing-traffic?rq=1

### Python使用指定端口进行http请求
#### 使用requests库
```python
class SourcePortAdapter(HTTPAdapter):
    """"Transport adapter" that allows us to set the source port."""

def __init__(self, port, *args, **kwargs):
        self.poolmanager = None
        self._source_port = port
        super().__init__(*args, **kwargs)

def init_poolmanager(self, connections, maxsize, block=DEFAULT_POOLBLOCK, **pool_kwargs):
        self.poolmanager = PoolManager(
            num_pools=connections, maxsize=maxsize,
            block=block, source_address=('', self._source_port))

s = requests.Session()
s.mount('https://baidu.com', SourcePortAdapter(54321))
s.get('https://baidu.com')
```
我用wireshark测试发现是走的54321端口。

#### 使用pycurl库
```python
c = pycurl.Curl()
c.setopt(c.URL, 'https://curl.haxx.se/dev/')
c.setopt(c.LOCALPORT, 54321)
c.setopt(c.LOCALPORTRANGE, [52314,56321,5532])
c.perform()
c.close()
```
测试OK，可以直接在curl命令行中测试。
```python
curl --local-port 12520 http://baidu.com
```