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INTERACTIVE LEARNING TOOL

Protocol Explorer · TCP

Explore internet protocols with animated messages, real arrival order and packet inspection.

Read the learning guides ↓
PROTOCOL EXPLORERLearn how the internet works
Now learningTCP · Reliable deliveryOverview · 5 steps
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0 / 14 complete · 0 in progress
Client192.168.1.10Router192.168.1.1InternetWeb Server203.0.113.10

Protocol overview

TCP

Active

Transmission Control Protocol

Build a reliable, ordered byte stream over an unreliable packet network. Observe connection setup, acknowledgement, retransmission and shutdown.

Layer
Transport (Layer 4)
Default port
Application dependent
Transport
IPv4 / IPv6
Data format
Ordered byte stream
Defined in
RFC 9293
Read the complete guide ↗

Packet flow

DNSTCPRequestResponse
No.TimeSourceDestinationProtocolInfoSize
10.000s192.168.1.10203.0.113.10TCP52344 → 80 [SYN] Seq=066 B
20.024s203.0.113.10192.168.1.10TCP80 → 52344 [SYN, ACK] Seq=0 Ack=166 B
30.048s192.168.1.10203.0.113.10TCP52344 → 80 [ACK] Seq=1 Ack=160 B
40.072s192.168.1.10203.0.113.10TCP52344 → 80 [PSH, ACK] Seq=1 Ack=1 Len=360 B
50.096s203.0.113.10192.168.1.10TCP80 → 52344 [ACK] Seq=1 Ack=460 B
60.120s192.168.1.10203.0.113.10TCP52344 → 80 [PSH, ACK] Seq=4 Ack=1 Len=360 B
70.144s192.168.1.10203.0.113.10TCP52344 → 80 [PSH, ACK] Seq=4 Ack=1 Len=3 · Retransmission60 B
80.168s203.0.113.10192.168.1.10TCP80 → 52344 [ACK] Seq=1 Ack=760 B
90.192s192.168.1.10203.0.113.10TCP52344 → 80 [FIN, ACK] Seq=7 Ack=160 B
100.216s203.0.113.10192.168.1.10TCP80 → 52344 [ACK] Seq=1 Ack=860 B
110.240s203.0.113.10192.168.1.10TCP80 → 52344 [FIN, ACK] Seq=1 Ack=860 B
120.264s192.168.1.10203.0.113.10TCP52344 → 80 [ACK] Seq=8 Ack=260 B

NAVSPROUT · PROTOCOL FIELD GUIDES

TCP, packet by packet.

Build a reliable, ordered byte stream over an unreliable packet network. Observe connection setup, acknowledgement, retransmission and shutdown.

PROTOCOL FIELD GUIDE

How TCP works

Build a reliable, ordered byte stream over an unreliable packet network. Observe connection setup, acknowledgement, retransmission and shutdown.

Default port
Application dependent
Transport / carrier
IPv4 / IPv6
Category
core

1. Synchronize sequence numbers

The client sends SYN with its initial sequence number. SYN consumes one sequence number even though it carries no application data here.

2. Acknowledge the handshake

The server replies SYN-ACK and the client acknowledges it. Both directions now have independent sequence spaces.

3. Deliver and acknowledge bytes

An ACK is cumulative: Ack=1004 means all bytes before 1004 have arrived in order. The advertised window limits outstanding data.

4. Recover a lost segment

A missing acknowledgement can trigger retransmission. Retransmitted bytes retain their sequence numbers so a receiver can discard duplicates.

5. Close both directions

FIN closes one sending direction and consumes a sequence number. The peer can finish its own data before closing the opposite direction.

Protocol relationships

Protocols cooperate across layers. Compare the neighboring lessons to distinguish addressing, delivery, application semantics and encryption.

Standards and editorial method

Written and implemented independently by NavSprout. Lessons summarize public protocol standards using synthetic documentation addresses and fictional credentials. Consult the standards for complete wire formats and normative behavior.

RFC 9293 ↗

Check your understanding

What does a TCP sequence number identify?

Why it’s hereNAVSPROUT ORIGINAL

Reading definitions is easier when you can connect them to a packet. This first-party learning tool pairs static explanations with a visual lab, byte inspection and a short knowledge check. All course data and application resources ship with NavSprout.

  1. Choose DNS and follow the lookup from client to authoritative server.
  2. Switch to the sequence view, then inspect a packet and select a field to highlight its bytes.
  3. Compare TCP with UDP, answer the quiz and export your progress.

Frequently asked questions

What happens when I open a website?

A typical first HTTPS visit can involve DNS resolution, a transport connection, a TLS handshake and an HTTP exchange. Caches, connection reuse and HTTP/3 can change this sequence.

How are TCP and UDP different?

TCP presents a reliable ordered byte stream. UDP preserves individual datagram boundaries without built-in delivery guarantees. Applications choose the behavior they need.

Are these real captured packets?

No. Frames are generated locally for teaching. Header lengths and checksums are calculated, while TLS ciphertext and some negotiation payloads are illustrative. Downloaded PCAP files contain synthetic examples, not live traffic.

Can I learn without JavaScript or an account?

All 14 protocol guides and their lesson explanations are available as ordinary HTML without signing in. JavaScript powers animations, byte inspection, local progress and quizzes.

Where is my progress saved?

Only in this browser’s local storage. Export a progress JSON file to move it to another device. Clearing browser data can remove progress.

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