How to creating a syn packet? Please help.

Discussion in 'Colasoft Free Network Tools' started by JayanK, Nov 5, 2009.

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  1. JayanK
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    JayanK Registered Member

    Hi,

    I am new to packet builder, I am trying to create a syn packet with the packet builder and it does not seem to work.

    1. Add a new TCP packet.
    2. Set the source IP.
    3. Set the destination IP.
    4. Set the source port.
    5. Set the destination port.
    6. Set the synchronize sequence flag to 1.
    7. Send the packet.

    All other values are default.

    But on the destination PC, the port does not open or any packets come through on the sniffer.

    Please help.

    Thanks,
    JK.
    Last edited: Nov 5, 2009
  2. Stem
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    Stem Firewall Expert

    Hi,

    You will also need to add the source/ destination MAC address.

    01.png

    You would find it easier to use a sniffer to capture an outbound connection (syn packet) from the PC, then save the capture and load it into the packet builder, then edit as needed


    - Stem
  3. allanon85
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    allanon85 Registered Member

    I'm pretty new to this software and also have difficulty creating a TCP syn packet.

    Can somebody kind enough to show the portion on how to set the synchronisation sequence flag correctly?

    What I see on screen is shown here, whats the correct way to set this flag to 1?

    Edit: pardon the crappy picture, my first time uploading stuff

    Attached Files:

  4. Colasoft Support
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    Colasoft Support Colasoft Moderator

    Dear all,

    In packet builder, you can just click the field to type a new value.

    We know TCP is 3-way handshake.

    1st handshake is a SYN packet: we need to set "synchronize sequence" field as 1, (others keept 0).

    2nd handshake is a ACK SYN packet: "Acknowledgment number" is set 1 and "synchronize sequence" 1.

    3rd handshake is a ACK packet: only "Acknowledgment number" is set 1.
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