ios - iOS 上的 webRTC : Can't send SDP answer, RTCPeerConnection.setRemoteDescription() 失败

Question

我正在使用随 cocoapods 安装的 libjingle_peerconnection。当我通过调用者的信令服务器收到 SDP 报价时，我试图将其设置为远程描述，这会触发 RTCSessionDescriptionDelegate peerConnection:didSetSessionDescriptionWithError:有错误:

Error Domain=RTCSDPError Code=-1 "(null)"UserInfo={error=Failed to set remote answer sdp: Called in wrong state: STATE_INIT}。

我的代码是:

- (void)transportChanell:(TransportChannel *)channel didReceivedSignalWithSessionDescription:(NSString *)sessionDescription withType:(NSString *)type {
    RTCSessionDescription *remoteDesc = [[RTCSessionDescription alloc] initWithType:@"answer" sdp:sessionDescription];
    [_peerConnection setRemoteDescriptionWithDelegate:self sessionDescription:remoteDesc];
}

我已经对这个问题进行了大量调查，并在 webRTC 源代码中找到了这个地方，正如我所想的那样，这个错误来自 BadRemoteSdp(type, BadStateErrMsg(state()), err_desc); WebRtcSession 的所有可能状态是:

    STATE_INIT = 0,
    STATE_SENTOFFER,         // Sent offer, waiting for answer.
    STATE_RECEIVEDOFFER,     // Received an offer. Need to send answer.
    STATE_SENTPRANSWER,      // Sent provisional answer. Need to send answer.
    STATE_RECEIVEDPRANSWER,  // Received provisional answer, waiting for answer.
    STATE_INPROGRESS,        // Offer/answer exchange completed.
    STATE_CLOSED,            // Close() was called.

有什么建议吗，我在调用者或被调用者方面可能会错过什么？

Answer 1

根据错误消息，该提议似乎被标记为“答案”。它失败了，因为它希望您处于 STATE_SENTOFFER 状态。

如果您已经创建了一个报价并发送给对方，您可能忘记先调用 setLocalDescription。如果您没有从失败的客户端发送报价，则应将对方更改为发送报价而不是答复。