The source and destination ports in the TCP headers

The TCP header, shown in the TCP chapter of Computer Networking: Principles, Protocols and Practice contains a source port and a destination port. The two segments below correspond to the beginning of a TCP connection.

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TCP source and destination ports

The first TCP segment was sent by a client to a server to establish a connection. From the response returned by the server, can you infer the source and destination ports used in the first segment ?

#	Length	Summary	Status
0	24 bytes	`Transmission Control Protocol, Src Port: ????, Dst Port: ????, Seq: 0, Len: 0`
1	24 bytes	`Transmission Control Protocol, Src Port: 1234, Dst Port: 53710, Seq: 0, Ack: 1, Len: 0`

0000 ????????c9613aec 0000000060027080
0010 00000000020405a0

0000 ????Éa:ì....`.p.
0010 ........

Transmission Control Protocol, Src Port: ????, Dst Port: ????, Seq: 0, Len: 0
- Source Port: ?
- Destination Port: ?
- Sequence number: 0 (relative sequence number)
- Acknowledgment number: 0
- 0110 .... = Header Length: 24 bytes (6)
- Flags
  - 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: 28800
- Urgent pointer: 0
- Options: (4 bytes), Maximum segment size
  - TCP Option - Maximum segment size: 1440 bytes
    - Kind: Maximum Segment Size (2)
    - Length: 4
    - MSS Value: 1440

0000 04d2d1ce93aaa513 c9613aed60127080
0010 00000000020405a0

0000 .ÒÑÎ.ª¥.Éa:í`.p.
0010 ........

Transmission Control Protocol, Src Port: 1234, Dst Port: 53710, Seq: 0, Ack: 1, Len: 0
- Source Port: 1234
- Destination Port: 53710
- Sequence number: 0 (relative sequence number)
- Acknowledgment number: 1 (relative ack number)
- 0110 .... = Header Length: 24 bytes (6)
- Flags
  - 000. .... .... = Reserved: Not set
  - ...0 .... .... = Nonce: Not set
  - .... 0... .... = Congestion Window Reduced (CWR): Not set
  - .... .0.. .... = ECN-Echo: Not set
  - .... ..0. .... = Urgent: Not set
  - .... ...1 .... = Acknowledgment: Set
  - .... .... 0... = Push: Not set
  - .... .... .0.. = Reset: Not set
  - .... .... ..1. = Syn: Set
  - .... .... ...0 = Fin: Not set
- Window size value: 28800
- Urgent pointer: 0
- Options: (4 bytes), Maximum segment size
  - TCP Option - Maximum segment size: 1440 bytes
    - Kind: Maximum Segment Size (2)
    - Length: 4
    - MSS Value: 1440

Author(s)	Olivier Bonaventure
Deadline	No deadline
Submission limit	No limitation
Category tags	tcp

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The source and destination ports in the TCP headers

TCP source and destination ports

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TCP source and destination ports

The source and destination ports in the TCP headers