用Wireshark抓取TCP和UDP头结构

在Wireshark中抓取TCP和UDP头结构，可以按照以下步骤进行：

1. 打开Wireshark，并选择要抓取的网络接口。
2. 在过滤器中输入过滤规则，如 `tcp` 或 `udp`，以过滤出 TCP 或 UDP 的数据包。
3. 点击“开始捕获”按钮，开始抓取数据包。
4. 在捕获到 TCP 或 UDP 数据包后，选中该数据包并展开“Transmission Control Protocol”或“User Datagram Protocol”标签，即可查看 TCP 或 UDP 头结构。

下面是TCP头结构的示例：

Transmission Control Protocol, Src Port: 49366, Dst Port: 80, Seq: 1, Ack: 1, Len: 0
    Source Port: 49366
    Destination Port: 80
    [Stream index: 0]
    [TCP Segment Len: 0]
    Sequence number: 1
    [Next sequence number: 1]
    Acknowledgment number: 1
    Header Length: 20 bytes
    Flags: 0x10 (ACK)
        000. .... .... = Reserved: Not set
        ...0 .... .... = Nonce: Not set
        .... 0... .... = Congestion Window Reduced (CWR): Not set
        .... .0.. .... = ECN-Echo: Not set
        .... ..0. .... = Urgent: Not set
        .... ...0 .... = Acknowledgment: Not set
        .... .... 0... = Push: Not set
        .... .... .0.. = Reset: Not set
        .... .... ..1. = Syn: Set
        .... .... ...0 = Fin: Not set
    Window size value: 64240
    [Calculated window size: 64240]
    Checksum: 0xb2a1 [unverified]
    [Checksum Status: Unverified]
    Urgent pointer: 0
    Options: (20 bytes)
        No-Operation (NOP)
        No-Operation (NOP)
        Timestamps: TSval 129214501 ecr 0
        NOP
        MSS: 1460

下面是UDP头结构的示例：

User Datagram Protocol, Src Port: 49366, Dst Port: 53
    Source Port: 49366
    Destination Port: 53
    Length: 55
    Checksum: 0x1e65 [unverified]
    [Checksum Status: Unverified]
    [Stream index: 0]
    [Timestamps]
        [Time since first frame: 0.000000000 seconds]
        [Time since previous frame: 0.000000000 seconds]