通过GB接入两个NVR，之后的播回放SIP报错503 #115
Description
ERROR GB28181 invite {"id": "31020010001130905317", "channel": "51000000001320000027", "error": "sip.RequestError: request failed with reason 'Service Unavailable (Code 503)'", "msg": "INVITE sip:51000000001320000027@10.102.50.100:5060 SIP/2.0\r\nVia: SIP/2.0/UDP 10.102.50.215:5060;branch=z9hG4bK.9vw80y7aY31V9gPVTOUCfK8sgJybOa5o\r\nFrom: sip:34020000002000000001@10.102.50.215:5060;tag=508384305\r\nTo: sip:51000000001320000027@10.102.50.100:5060\r\nCall-ID: 2429023261\r\nUser-Agent: Monibuca\r\nCSeq: 20 INVITE\r\nMax-Forwards: 70\r\nContact: sip:34020000002000000001@10.102.50.215:5060;tag=508384305\r\nContent-Type: application/sdp\r\nContent-Length: 254\r\nSubject: 51000000001320000027:1200001716,34020000002000000001:0\r\nAllow: INVITE, ACK, CANCEL, NOTIFY, BYE, REGISTER, MESSAGE\r\n\r\nv=0\r\no=51000000001320000027 0 0 IN IP4 10.102.50.215\r\ns=Playback\r\nu=51000000001320000027:0\r\nc=IN IP4 10.102.50.215\r\nt=1722355200 1722355579\r\nm=video 58234 TCP/RTP/AVP 96\r\na=recvonly\r\na=rtpmap:96 PS/90000\r\ny=1200001716\r\na=setup:passive\r\na=connection:new\r\n"}