PythonでSIPサーバーと送受信

Pythonのsocketを使用してUDP通信でSIPサーバーにREGISTER リクエストを行い、IP アドレスを SIPサーバーに登録します。

IP電話がUDPプロトコルを使用する理由
　UDP (User Datagram Protocol) は、データを送るだけのシンプルなプロトコルです。他のプロトコルに比べてデータが正しく届いたかを確認する仕組みを省略し、信頼性や確実性よりも速度(リアルタイム性)を重視の動画や音声のストリーミング、オンラインゲームなどに使用されるプロトコルです。UDP通信プロトコルはIP電話に適しています。

Pythonのsocket()関数を使用したUDPの通信の流れは以下のとおりです。

サーバー(SIPサーバー)    クライアント(IP電話)
【socket()】                【socket()】   ソケットを作成する
   ↓                           ↓
【bind()】                                待受けIPアドレスとポート番号を設定する
   ↓
【recvfrom()】  <-- データ   【sendto()】   クライアントからサーバーに送信する
   ↓                           ↓
【sendto()】    データ -->   【recv()】     サーバーからクライアントに送信する
   ↓                           ↓
【close()】                 【close()】    ソケットを閉じる

---

クライアント(IP電話)側のUDPを使った簡単なネットワークプログラミング

udp_client.py

#!/usr/bin/python3

import socket

HOST = "192.168.0.201"
PORT = 5060

# 送信文字列(ソフトフォン起動時にSIPサーバーに送信した内容をWiresharkで入手)
MESSAGE = '''REGISTER sip:192.168.0.201 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.41:5060;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Max-Forwards: 70
Contact: <sip:20@192.168.0.41>
To: <sip:20@192.168.0.201>
From: <sip:20@192.168.0.201>;tag=b50e84ed
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
CSeq: 1 REGISTER
Expires: 3600
Content-Length: 0'''

# ソケット作成
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# メッセージ送信
sock.sendto(MESSAGE.encode('utf-8'), (HOST, PORT))
print('Sent message >>>>>')
print('====================')
print(MESSAGE)
print('====================')

# メッセージ受信
recv_message = sock.recv(1024)

print(f'Received message >>>>>')
print('====================')
print(recv_message.decode('utf-8'))
print('====================')

# ソケットを閉じる
sock.close()

udp_client.pyの実行結果(Asterisk起動している前提)

Sent message >>>>>
====================
REGISTER sip:192.168.0.201 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.41:5060;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Max-Forwards: 70
Contact: <sip:20@192.168.0.41>
To: <sip:20@192.168.0.201>
From: <sip:20@192.168.0.201>;tag=b50e84ed
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
CSeq: 1 REGISTER
Expires: 3600
Content-Length: 0
====================
Received message >>>>>
====================
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 192.168.0.41:5060;rport=58482;received=192.168.0.201;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
From: <sip:20@192.168.0.201>;tag=b50e84ed
To: <sip:20@192.168.0.201>;tag=z9hG4cK6b86b273ff34fce19d6b804ef
CSeq: 1 REGISTER
WWW-Authenticate: Digest realm="asterisk",nonce="1763994373/8074807feebaac3410e79cb9f9586de0",opaque="0f8adef278a327a1",algorithm=MD5,qop="auth"
Server: Asterisk PBX 23.0.0
Content-Length:  0


====================

SIPサーバーとクライアントPCのシーケンス

      内線20                         SIPサーバー
      IP:192.168.0.41                IP:192.168.0.201

         |                              |
         |(1) REGISTER                  |
         |----------------------------->|
         |(2) 401 Unauthorized          |
         |<-----------------------------|
         |                              |

SIPサーバーへのUDP 5060番ポートで「REGISTER」を送信するとSIPサーバーから「401 Unauthorized」が返信される。

---

SIPサーバーに内線20を登録して着信可能にするコードを紹介します。

設定内容
　SIPサーバーIP:「192.168.0.201」
　ポート:「5060」

　ソフトフォンID:「21」

　自分IP:「192.168.0.41」
　自分ID:「20」
　パスワード:「pass」

sip_client.py

#!/usr/bin/python3

import socket
import sys
import re
import signal
import random
import hashlib

SERVER_IP = '192.168.0.201' #SIPサーバーアドレス
MY_IP = '192.168.0.41' #自分のIPアドレス

PORT = 5060 

ID = '20' #ID
PASS = 'pass' #パスワード

class Counter():
  def __init__(self, start=1):
    self.i = start
    
  def next(self):
    i = self.i
    self.i += 1
    return i

class SIP_message():
  def __init__(self, data):
    self.status = 0
    self.headers = {}
    self.parse(data)

  def parse(self, data):
    headers = data.split(b'\r\n\r\n')[0]
    header = headers.split(b'\r\n')
    
    if str(header[0].split(b" ")[0], 'utf8') in ['SIP/2.0']:
      self.version = str(header[0].split(b" ")[0], 'utf8') 
      self.status = int(header[0].split(b" ")[1])
      
    elif str(header[0].split(b" ")[0], 'utf8') in ['INVITE', 'ACK', 'BYE', 'CANCEL']:
      self.version = str(header[0].split(b" ")[2], 'utf8')
      self.method = str(header[0].split(b" ")[0], 'utf8')

    headers = {}
        
    for x in header[1:]:
      row = str(x, 'utf8').split(': ')
      headers[row[0]] = row[1]
      
    for x in headers:
      self.parseHeader(x, headers[x])

  def parseHeader(self, header, data):
    if header=="Via":
      split_data = re.split(" |;", data)
      self.headers['Via'] = {'type': split_data[0], 'address': split_data[1]}
      for x in split_data[2:]: 
        if '=' in x:
          self.headers['Via'][x.split('=')[0]] = x.split('=')[1]
        else:
          self.headers['Via'][x] = None
    elif header=="From" or header=="To":
      split_data = data.split(';tag=')
      tag = ''
      if len(split_data) >= 2:
        tag = split_data[1]
      sip_url = split_data[0]
      
      self.headers[header] = {'sip_url': sip_url, 'tag': tag}
    elif header=="CSeq":
      self.headers[header] = {'check': data.split(" ")[0], 'method': data.split(" ")[1]}
    elif header=="Allow" or header=="Supported":
      self.headers[header] = data.split(", ")
    elif header=="Content-Length":
      self.headers[header] = int(data)
    elif header=='WWW-Authenticate':
      data = data.replace("Digest", "")
      split_data = data.split(",")
      header_data = {}
      for x in split_data:
        x = x.strip()
        header_data[x.split('=')[0]] = x.split('=')[1].strip('"')
      self.headers[header] = header_data
    else:
      self.headers[header] = data

class SIP_connect():
    def __init__(self, server, port, username, password, myIP):
        self.server = server
        self.port = port
        self.myIP = myIP
        self.username = username
        self.password = password
        self.tags = []
        self.tagLibrary = {}
        self.registerCounter = Counter()
        self.callID = Counter()
        
    def genCallID(self):
        return hashlib.sha256(str(self.callID.next()).encode('utf8')).hexdigest()[0:32]+"@"+self.myIP+":"+str(self.port)
    
    def Tag(self):
        while True:
            tag = hashlib.md5(str(random.randint(1, 4294967296)).encode('utf8')).hexdigest()[0:8]
            if tag not in self.tags:
                self.tags.append(tag)
                return tag

    def Authorization(self, response):
        HA1 = hashlib.md5(self.username.encode('utf8')+b':'+response.headers['WWW-Authenticate']['realm'].encode('utf8')+b':'+self.password.encode('utf8')).hexdigest().encode('utf8')
        HA2 = hashlib.md5(response.headers['CSeq']['method'].encode('utf8')+b':sip:'+self.server.encode('utf8')).hexdigest().encode('utf8')
        nonce = response.headers['WWW-Authenticate']['nonce'].encode('utf8')
        result = hashlib.md5(HA1+b':'+nonce+b':'+HA2).hexdigest().encode('utf8')
   
        return result
        
    def Register(self, response): 
        if response == '':
            branch = "z9hG4cK"+self.genCallID()[0:25]
            call_id = self.genCallID()
        else:
            result = self.Authorization(response)
            branch = response.headers['Via']['branch']
            call_id = response.headers['Call-ID']
            nonce = response.headers['WWW-Authenticate']['nonce']
            realm = response.headers['WWW-Authenticate']['realm']
        
        message = "REGISTER sip:"+self.server
        message += " SIP/2.0\r\nVia: SIP/2.0/UDP "+self.myIP+":"+str(self.port)+";branch="+branch
        message += "\r\nMax-Forwards: 70\r\nContact: \r\nFrom: ;tag="+self.Tag()
        message += "\r\nCall-ID: "+call_id
        message += "\r\nCSeq: "+str(self.registerCounter.next())+" REGISTER"
        message += "\r\nExpires: 3600\r\n"

        if response != '':
            message += 'Authorization: Digest username="'+self.username
            message += '",realm="'+realm+'",nonce="'+nonce
            message += '",uri="sip:'+self.server
            message += '",response="'+str(result, 'utf8')+'"\r\n'
            
        message += "Content-Length: 0\r\n\r\n"
        
        return message
    
    def Trying(self, response):
        message = "SIP/2.0 100 Trying\r\n"
        message += "Via: SIP/2.0/UDP "+response.headers['Via']['address']+";branch="+response.headers['Via']['branch']+"\r\n"
        message += "From: "+response.headers['From']['sip_url']+";tag="+response.headers['From']['tag']+"\r\n"
        message += "To: "+response.headers['To']['sip_url']+"\r\n"
        message += "Call-ID: "+response.headers['Call-ID']+"\r\n"
        message += "CSeq: "+response.headers['CSeq']['check']+" "+response.headers['CSeq']['method']+"\r\n"
        message += "Max-Forwards: 70\r\n"
        message += "Content-Length: 0\r\n\r\n"
        
        return message

    def Ringing(self, response,tag):
        message = "SIP/2.0 180 Ringing\r\n"
        message += "Via: SIP/2.0/UDP "+response.headers['Via']['address']+";branch="+response.headers['Via']['branch']+"\r\n"
        message += "From: "+response.headers['From']['sip_url']+";tag="+response.headers['From']['tag']+"\r\n"
        message += "To: "+response.headers['To']['sip_url']+";tag="+tag+"\r\n"
        message += "Call-ID: "+response.headers['Call-ID']+"\r\n"
        message += "CSeq: "+response.headers['CSeq']['check']+" "+response.headers['CSeq']['method']+"\r\n"
        message += "Contact: \r\n"
        message += "Content-Length: 0\r\n\r\n" 
        self.tagLibrary[response.headers['Call-ID']] = tag
        
        return message

    def Ok(self, response):
        message = "SIP/2.0 200 OK\r\n"
        message += "Via: SIP/2.0/UDP "+response.headers['Via']['address']+";branch="+response.headers['Via']['branch']+"\r\n"
        message += "From: "+response.headers['From']['sip_url']+";tag="+response.headers['From']['tag']+"\r\n"
        message += "To: "+response.headers['To']['sip_url']+";tag="+response.headers['To']['tag']+"\r\n"
        message += "Call-ID: "+response.headers['Call-ID']+"\r\n"
        message += "CSeq: "+response.headers['CSeq']['check']+" "+response.headers['CSeq']['method']+"\r\n"
        message += "Content-Length: 0\r\n\r\n"
        
        return message
      
    def Ack(self, response):
        tag = self.tagLibrary[response.headers['Call-ID']]
        message = "ACK "+response.headers['To']['sip_url'].strip('<').strip('>')+" SIP/2.0\r\n"
        message += "Via: SIP/2.0/UDP "+self.myIP+":"+str(self.port)+";branch="+response.headers['Via']['branch']+"\r\n"
        message += "Max-Forwards: 70\r\n"
        if response.headers['To']['tag'] == '':
            message += "To: "+response.headers['To']['sip_url']+"\r\n"
        else:
            message += "To: "+response.headers['To']['sip_url']+";tag="+response.headers['To']['tag']+"\r\n"
        message += "From: "+response.headers['From']['sip_url']+";tag="+tag+"\r\n"
        message += "Call-ID: "+response.headers['Call-ID']+"\r\n"
        message += "CSeq: "+str(response.headers['CSeq']['check'])+" ACK\r\n"
        message += "Content-Length: 0\r\n\r\n"
    
        return message
            
    def start(self):
    
       #ctl+c#
        signal.signal(signal.SIGINT, signal.SIG_DFL)
        self.s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        
        try:
            self.s.bind((self.myIP, self.port))
        except OSError as e:
            print(e)

        response = ""

        message = self.Register(response)
        print(message)
        self.s.sendto(message.encode('utf8'), (self.server, self.port))

        readbuf = self.s.recv(8192)
        response = SIP_message(readbuf)
        print(readbuf.decode('utf-8'))

        message = self.Register(response)
        print(message)
        self.s.sendto(message.encode('utf8'), (self.server, self.port))

        readbuf = self.s.recv(8192)
        response = SIP_message(readbuf)
        print(readbuf.decode('utf-8'))

        while True:
            readbuf = self.s.recv(8192)
            print(readbuf.decode('utf-8'))
            response = SIP_message(readbuf)
            
            if response.headers['CSeq']['method'] == 'INVITE' and response.headers['Content-Length'] != 0:
                sip_url = response.headers['From']['sip_url']
                phone_num = re.search(r'sip:(.*)@',sip_url).group(1)
                
                call_id_buf = re.search(r'(.*)@',response.headers['Call-ID'])
                if call_id_buf is None:
                  call_id = response.headers['Call-ID']
                else:
                  call_id = call_id_buf.group(1)
                
                print('###################')
                print('Incoming number=',phone_num)
                print('###################')
                
                trying = self.Trying(response)
                self.s.sendto(trying.encode('utf8'), (self.server, self.port))
                print(trying)
                tag = self.Tag()
                ringing = self.Ringing(response,tag)
                self.s.sendto(ringing.encode('utf8'), (self.server, self.port))
                print(ringing)

            elif response.headers['CSeq']['method'] == 'CANCEL':
                ok = self.Ok(response)
                self.s.sendto(ok.encode('utf8'), (self.server, self.port))
                print(ok)

        s.close()

sip = SIP_connect(SERVER_IP, PORT, ID, PASS, MY_IP)

sip.start()

sip_client.pyの実行結果(Asterisk起動している前提)

SIPサーバーにソフトフォン内線21を登録する。
↓
SIPサーバーに自分内線20を登録する。
↓
ソフトフォン内線21がら内線20に電話をかける。
↓
ソフトフォン内線21がら内線20の呼出しを止める。

REGISTER sip:192.168.0.201 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.41:5060;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Max-Forwards: 70
Contact: <sip:20@192.168.0.41>
To: <sip:20@192.168.0.201>
From: <sip:20@192.168.0.201>;tag=5cc014e4
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
CSeq: 1 REGISTER
Expires: 3600
Content-Length: 0


SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 192.168.0.41:5060;rport=5060;received=192.168.0.41;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
From: <sip:20@192.168.0.201>;tag=5cc014e4
To: <sip:20@192.168.0.201>;tag=z9hG4cK6b86b273ff34fce19d6b804ef
CSeq: 1 REGISTER
WWW-Authenticate: Digest realm="asterisk",nonce="1768112133/88d496d35b71d7dd9b449e4892cbd71c",opaque="6f3e8fba6e7d9a17",algorithm=MD5,qop="auth"
Server: Asterisk PBX 23.0.0
Content-Length:  0



REGISTER sip:192.168.0.201 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.41:5060;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Max-Forwards: 70
Contact: <sip:20@192.168.0.41>
To: <sip:20@192.168.0.201>
From: <sip:20@192.168.0.201>;tag=c205ddd4
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
CSeq: 2 REGISTER
Expires: 3600
Authorization: Digest username="20",realm="asterisk",nonce="1768112133/88d496d35b71d7dd9b449e4892cbd71c",uri="sip:192.168.0.201",response="f117c90fc8812415eec31580fbeaaec6"
Content-Length: 0


SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.0.41:5060;rport=5060;received=192.168.0.41;branch=z9hG4cK6b86b273ff34fce19d6b804ef
Call-ID: d4735e3a265e16eee03f59718b9b5d03@192.168.0.41:5060
From: <sip:20@192.168.0.201>;tag=c205ddd4
To: <sip:20@192.168.0.201>;tag=z9hG4cK6b86b273ff34fce19d6b804ef
CSeq: 2 REGISTER
Date: Sun, 11 Jan 2026 06:15:33 GMT
Contact: <sip:20@192.168.0.41>;expires=3599
Expires: 3600
Server: Asterisk PBX 23.0.0
Content-Length:  0



INVITE sip:20@192.168.0.41 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.201:5060;rport;branch=z9hG4bKPjc42f673a-1751-4623-a8bd-48c3aa305c79
From: "21" <sip:21@192.168.0.201>;tag=aa435736-c3b2-4ba1-a00e-5ceeb79d3e3d
To: <sip:20@192.168.0.41>
Contact: <sip:asterisk@192.168.0.201:5060>
Call-ID: d2c00c2d-7114-4440-bb1c-a216954d11e9
CSeq: 10033 INVITE
Allow: OPTIONS, REGISTER, SUBSCRIBE, NOTIFY, PUBLISH, INVITE, ACK, BYE, CANCEL, UPDATE, PRACK, INFO, MESSAGE, REFER
Supported: 100rel, timer, replaces, norefersub, histinfo
Session-Expires: 1800
Min-SE: 90
Max-Forwards: 70
User-Agent: Asterisk PBX 23.0.0
Content-Type: application/sdp
Content-Length:   237

v=0
o=- 506936747 506936747 IN IP4 192.168.0.201
s=Asterisk
c=IN IP4 192.168.0.201
t=0 0
m=audio 11548 RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=maxptime:140
a=sendrecv


###################
Incoming number= 21
###################


SIP/2.0 100 Trying
Via: SIP/2.0/UDP 192.168.0.201:5060;branch=z9hG4bKPjc42f673a-1751-4623-a8bd-48c3aa305c79
From: "21" <sip:21@192.168.0.201>;tag=aa435736-c3b2-4ba1-a00e-5ceeb79d3e3d
To: <sip:20@192.168.0.41>
Call-ID: d2c00c2d-7114-4440-bb1c-a216954d11e9
CSeq: 10033 INVITE
Max-Forwards: 70
Content-Length: 0


SIP/2.0 180 Ringing
Via: SIP/2.0/UDP 192.168.0.201:5060;branch=z9hG4bKPjc42f673a-1751-4623-a8bd-48c3aa305c79
From: "21" <sip:21@192.168.0.201>;tag=aa435736-c3b2-4ba1-a00e-5ceeb79d3e3d
To: <sip:20@192.168.0.41>;tag=006c7dc6
Call-ID: d2c00c2d-7114-4440-bb1c-a216954d11e9
CSeq: 10033 INVITE
Contact: <sip:20@192.168.0.41>
Content-Length: 0


CANCEL sip:20@192.168.0.41 SIP/2.0
Via: SIP/2.0/UDP 192.168.0.201:5060;rport;branch=z9hG4bKPjc42f673a-1751-4623-a8bd-48c3aa305c79
From: "21" <sip:21@192.168.0.201>;tag=aa435736-c3b2-4ba1-a00e-5ceeb79d3e3d
To: <sip:20@192.168.0.41>
Call-ID: d2c00c2d-7114-4440-bb1c-a216954d11e9
CSeq: 10033 CANCEL
Reason: Q.850;cause=127
Max-Forwards: 70
User-Agent: Asterisk PBX 23.0.0
Content-Length:  0


SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.0.201:5060;branch=z9hG4bKPjc42f673a-1751-4623-a8bd-48c3aa305c79
From: "21" <sip:21@192.168.0.201>;tag=aa435736-c3b2-4ba1-a00e-5ceeb79d3e3d
To: <sip:20@192.168.0.41>;tag=
Call-ID: d2c00c2d-7114-4440-bb1c-a216954d11e9
CSeq: 10033 CANCEL
Content-Length: 0

SIPサーバーと内線電話のシーケンス

             内線20                    SIPサーバー               内線21

              |                          |                          |
              |                          |    REGISTER no sdp       |
              |                          |<-------------------------|
              |                          |    401 Unauthorized      |
              |                          |------------------------->|
              |                          |    REGISTER no sdp PA    |
              |                          |<-------------------------|
              |                          |    200 OK                |
              |                          |------------------------->|
              |(1) REGISTER no sdp       |                          |
              |------------------------->|                          |
              |(2) 401 Unauthorized      |                          |
              |<-------------------------|                          |
              |(3) REGISTER no sdp PA    |                          |
              |------------------------->|                          |
              |(4) 200 OK                |                          |
              |<-------------------------|                          |
              |                          |    INVITE no sdp         |内線20を呼出す
              |                          |<-------------------------|
              |                          |    401 PAR               |
              |                          |------------------------->|
              |                          |    ACK                   |
              |                          |<-------------------------|
              |                          |    INVITE sdp PA         |
              |                          |<-------------------------|
内線20から着信|(5) INVITE sdp            |                          |
              |<-------------------------|                          |
              |(6) 100 Trying            |                          |
              |------------------------->|                          |
              |                          |    100 Trying            |
              |                          |------------------------->|
              |(7) 180 Ringing           |                          |
              |------------------------->|                          |
              |                          |    180 Ringing           |
              |                          |------------------------->|
              |                          |                          |
              |                          |    CANCEL                |呼出を止める
              |                          |<-------------------------|
  呼出が止まる|(8) CANCEL                |                          |
              |<-------------------------|                          |
              |(9) 200 OK                |                          |
              |------------------------->|                          |
              |                          |    200 OK                |
              |                          |------------------------->|
              |                          |                          |

着信番号は、INVITEの「From: “21” <sip:21@192.168.0.201>」の「21」です。

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