TCP vs UDP: When to Use What, and How TCP Relates to HTTP

What are TCP and UDP ?

Protocols help to connect one computer to another computer/server for talk . These are standard rules in which computer tells that how data will transfer. Without these rules user/server cannot understand the data language, who and what is sending, and there will be no privacy, that`s why they use Http.

There are a Lot of Protocols but We will focus on two protocols

i) TCP ii) UDP

Server can send data packets to the client through TCP and UDP .

TCP ( Transmission Control Protocol )

i) This is very Reliable. It transfer data from server to client very carefully and completely.

ii) It transfer data in the same order from server to client without changing or lossing any data packet. It also detect loss of data packets.

iii) It delivers data packets slowly compared to UDP .

iv) It does a synchronous acknowledgment. (3 way Handshake at start and end).

When to use TCP

Use TCP when you want to transfer data completely and in order ( delivery > speed ). It is mostly used for,

• Websites

• Emails

• File transfer

• Chat apps (WhatsApp, Telegram, etc.)

• Banking / payment apps

• APIs

Example:
If one byte of bank transaction is lost, whole transaction will be wrong → so TCP is used.

UDP ( User Datagram Protocol ) :

i) This is not Reliable , also it does not detect loss data packets and also do not deliver data in the order.

ii) It deliver data packets with very fast speed compared to TCP but with less control .

iii) It does Asynchronous acknowledge. (no handshake, direct data transfer).

When to use UDP

Use UDP when speed is more important than 100% delivery ( delivery < speed ):

• Live video calls (Zoom, Meet, WhatsApp video)

• Online gaming (PUBG, Free Fire, etc.)

• Live streaming (YouTube Live, Twitch)

• DNS queries (very small, can be re-sent if lost)

• VoIP (Voice over IP, e.g., WhatsApp calls)

Example:
If one frame in live video is lost, just a small glitch appears → but next frame comes → so UDP is used.

HTTP = Postman (What send - letter, parcel, etc.)

TCP = Secure courier ( How send - carefully with guarantee )

UDP = Fast delivery bike ( How send - quickly, no guarantee )

IP = Road system ( Where send - which path through )

HTTP is a protocol in which standardized data format (text-based, structured communication). TCP and UDP both work on the upper Layer of the HTTP layer. They define how the data will transferred (reliably or quickly). HTTP, TCP, and above work for web browsing.