一个数据包可以包含几个Websocket吗?

Question

我正在使用Wireshark检查服务器和浏览器之间的websocket流量时，我注意到这样的帧:

No.     Time           Source          Destination   Protocol  Length Info
 144342 8212.033150000 127.0.0.1       127.0.0.1     WebSocket 821    WebSocket Text [FIN] 
Frame 144342: 821 bytes on wire (6568 bits), 821 bytes captured (6568 bits) on interface 0
Ethernet II, Src: 00:00:00_00:00:00 (00:00:00:00:00:00), Dst: 00:00:00_00:00:00 (00:00:00:00:00:00)
Internet Protocol Version 4, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1)
Transmission Control Protocol, Src Port: http-alt (8080), Dst Port: 53749 (53749), Seq: 1132, Ack: 603, Len: 755
WebSocket
    1... .... = Fin: True
    .000 .... = Reserved: 0x00
    .... 0001 = Opcode: Text (1)
    0... .... = Mask: False
    .111 1110 = Payload length: 126 Extended Payload Length (16 bits)
    Extended Payload length (16 bits): 140
    Payload
        Text: {"type":"COLLABORATIVE_COMMANDS","remoteUser":"null","key":"1c78c08f-5d2d-445a-a63c-3a211d2f0336","messageBroadcast":{"smartPath":["null"]}}
WebSocket
    1... .... = Fin: True
    .000 .... = Reserved: 0x00
    .... 0001 = Opcode: Text (1)
    0... .... = Mask: False
    .111 1110 = Payload length: 126 Extended Payload Length (16 bits)
    Extended Payload length (16 bits): 329
    Payload
        Text [truncated]: {"type":"COLLABORATIVE_COMMANDS","remoteUser":"","key":"1c78c08f-5d2d-445a-a63c-3a211d2f0336","messageBroadcast":{"cameraInfos":{"target":{"x":0,"y":0,"z":0},"camPos":{"x":557.0133301398326,"y":159.5460628202445,"z":342.4
WebSocket
    1... .... = Fin: True
    .000 .... = Reserved: 0x00
    .... 0001 = Opcode: Text (1)
    0... .... = Mask: False
    .111 1110 = Payload length: 126 Extended Payload Length (16 bits)
    Extended Payload length (16 bits): 141
    Payload
        Text: {"type":"COLLABORATIVE_COMMANDS","remoteUser":"","key":"1c78c08f-5d2d-445a-a63c-3a211d2f0336","messageBroadcast":{"colourEditedMeshes":true}}
WebSocket
    1... .... = Fin: True
    .000 .... = Reserved: 0x00
    .... 0001 = Opcode: Text (1)
    0... .... = Mask: False
    .111 1110 = Payload length: 126 Extended Payload Length (16 bits)
    Extended Payload length (16 bits): 129
    Payload
        Text: {"type":"COLLABORATIVE_COMMANDS","remoteUser":"","key":"1c78c08f-5d2d-445a-a63c-3a211d2f0336","messageBroadcast":{"explode":"0"}}

这是否意味着我的数据包中有几个websockets ?这怎么可能呢?

Answer 1

如果你阅读WebSocket规范，RFC 6455，你会看到WebSocket数据包是帧的，其中每个帧都有自己的报头和有效负载。请记住，TCP是一种流传输。发送方和接收方并不关注TCP帧，他们关注的是这些帧内的有效载荷。WebSocket发送者将发送一个WebSocket头和它的有效载荷，然后是下一个WebSocket头和它的有效载荷，依此类推。WebSocket接收器将读取一个WebSocket报头及其有效载荷，然后读取下一个WebSocket报头及其有效载荷，依此类推。通常，在TCP套接字上启用Nagle算法，它将根据需要将应用程序数据拆分和组合到TCP帧中，以实现高效的网络传输。这是由对应用程序透明的TCP堆栈处理的。所以，是的，在一个TCP帧中出现多个WebSocket帧是可能的，如果这就是Nagle决定传输它们的方式的话。如果WebSocket数据包是在短时间内发送的，Nagle可能会合并它们，这样它只需要传输一个TCP帧，而不是单独的TCP帧。