Unix Network Programming Volume 1

Chapter 1

Chapter 2 TCP

Server passive open (passive open): Socket, bind, listen. The client is actively opened via the socket, connect (active open). Accept and connect are blocked

UDP UDP can be a full-duplex Chapter 3 - byte sort function

Low-order bytes are stored in the start Address: small End (Little-endian) byte order; high-order bytes are stored in the start address: big-endian (Big-endian) byte order. The Internet protocol uses big-endian byte-order to transmit these multibyte integers.

byte manipulation functions

#include <string.h>

//Set the specified number of bytes in the destination byte string to c
void *memset (void *dest, int c, size_t len);

Moves the specified number of bytes from the original byte to the target string
void *memcpy (void *dest, const void *SRC, size_t nbytes);

Compare byte strings, return the same 0
int memcpy (const void *ptrl, const void *PTR2, size_t nbytes);

Readn, writen, ReadLine functions

A byte-stream socket call read or write input or output may have fewer bytes than requested, however this is not a faulted state because the buffer used for sockets in the kernel has reached its limit.

Text line-based network protocol: SMTP, HTTP, FTP, etc. Chapter 4

fork and EXEC functions

#include <unistd.h>

//child process returns 0, the parent process returns the child process ID
pid_t fork (void);

Exec replaces the current process image with a new program file, the process ID is unchanged

The 6 exec functions are different:

Concurrent Server Profiles

Why does the parent process call close to CONNFD does not terminate its link to the customer? Because each file or socket has a reference count:

Most TCP servers are concurrent, and they derive a child process for each pending client link call fork. Most UDP servers are iterative.