<![CDATA[TCP Working: 3-Way Handshake]]>https://tcpworking3wayhandshakebyyashveer.hashnode.devRSS for NodeMon, 09 Nov 2026 12:40:17 GMT60<![CDATA[TCP Working: 3-Way Handshake & Reliable Communication]]>https://tcpworking3wayhandshakebyyashveer.hashnode.dev/tcp-working-3-way-handshake-and-reliable-communicationhttps://tcpworking3wayhandshakebyyashveer.hashnode.dev/tcp-working-3-way-handshake-and-reliable-communicationThu, 29 Jan 2026 14:05:38 GMTWhat we are studying in this article :

  1. What is TCP and why it is needed

  2. Problems TCP is designed to solve

  3. What is the TCP 3-Way Handshake

  4. Step-by-step working of SYN, SYN-ACK, and ACK

  5. How data transfer works in TCP

  6. How TCP ensures reliability, order, and correctness

  7. How a TCP connection is closed

1. What is TCP and why it is needed

TCP (Transmission Control Protocol) is a transport-layer protocol that provides reliable communication between applications over a network.

Why TCP is needed

The Internet (IP layer) is unreliable:

  • Packets can be lost

  • Packets can arrive out of order

  • Packets can be duplicated

  • No guarantee packets reach the destination

TCP fixes these problems, so applications don’t have to.

2. Problems TCP is designed to solve

TCP solves the following problems:

  • Packet loss → Retransmission

  • Out-of-order delivery → Sequencing

  • Duplicate packets → Duplicate detection

  • Network congestion → Flow & congestion control

  • Unknown delivery status → Acknowledgments

3. What is the TCP 3-Way Handshake

The 3-Way Handshake is how TCP:

  • Establishes a connection

  • Synchronizes sequence numbers

  • Confirms both sides are ready

Why 3 steps?

To ensure both sender and receiver agree to communicate and know each other’s initial sequence numbers.

4. Step-by-step working of SYN, SYN-ACK, and ACK

Step 1: SYN

  • Client sends SYN

  • Says: “I want to connect”

  • Includes initial sequence number (x)

Step 2: SYN-ACK

  • Server responds with SYN + ACK

  • Says: “I accept + here’s my sequence number (y)”

  • Acknowledges client’s SYN (x+1)

Step 3: ACK

  • Client sends ACK

  • Acknowledges server’s SYN (y+1)

5. How data transfer works in TCP

  • Data is split into segments

  • Each segment has a sequence number

  • Receiver sends ACKs for received data

6. How TCP ensures reliability, order, and correctness

Reliability

Ordered delivery

Correctness

Flow control

Congestion control

7. How a TCP connection is closed

Step-by-step:

  1. One side sends FIN (no more data)

  2. Other side sends ACK

  3. Other side sends its own FIN

  4. First side sends ACK

Both sides agree to close

]]>