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Asked: 2026-05-27T22:45:02+00:00

I’m working on a packet capture program. Is it possible for TCP packet to

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I’m working on a packet capture program. Is it possible for TCP packet to have the FIN flag set but also have data?

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  1. Editorial Team

    Strictly speaking, it is possible to put data in a TCP FIN packet… Quoting from RFC 793 (emphasis mine):

    The SYN and FIN
    are the only controls requiring this protection, and these controls
    are used only at connection opening and closing. For sequence number
    purposes, the SYN is considered to occur before the first actual data
    octet of the segment in which it occurs, while the FIN is considered
    to occur after the last actual data octet in a segment in which it
    occurs    .

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