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Implement a UDP Client and Server Using Only Syscalls

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PrevImplement the TCP 3-Way Handshake Using Raw Sockets

Language

Compiler

2.0s Limit 256MB

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Implementation

Implement a UDP client and server using only raw syscalls.

Requirements:

Create UDP socket with socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
Manually fill sockaddr_in with sin_family, sin_port (htons), sin_addr
Bind server socket to a port using bind()
Use sendto() to send datagrams
Use recvfrom() to receive datagrams
Show sockaddr_in fields after initialization
Print the syscall flow: socket -> bind -> sendto -> recvfrom
Demonstrate both client and server concepts in one program
Handle errors for each syscall

Why This Matters

Every DNS resolver, DHCP client, and syslog daemon on Linux ultimately calls socket(AF_INET, SOCK_DGRAM, 0) and manually fills sockaddr_in exactly as you do here, since getaddrinfo() is just a convenience wrapper around this same syscall sequence. Forgetting htons() on the port field is a real, extremely common bug — the value silently becomes garbage on little-endian machines instead of erroring.

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Validation Suite

main.c

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