Linux Network programming------Foundation of Network programming

Socket (socket), similar to file descriptor, three kinds

1, streaming Sockets (SOCK_STREAM): can provide a reliable, connection-oriented traffic flow, it uses the TCP protocol. TCP guarantees the correctness and sequencing of data transmission.

2. Datagram Sockets (SOCK_DGRAM): Defines a non-connected service that transmits data through separate messages, is unordered, and is not guaranteed to be reliable and error-free, using Datagram Protocol (UDP).

3, the original socket (SOCK_RAW): Directly based on the IP protocol.

Network address

The struct sockaddr is used to record network addresses:

struct SOCKADDR

{

U_short sa_family;//protocol family, using "af_xxx" form, such as: Af_inet (IP protocol family)

Char SA_DATA[14];//14 byte-specific protocol address

}

But the most common is the SOCKADDR_IN record network address

struct SOCKADDR_IN

{

Short int sin_family;//Protocol family

unsigned short int sin_port;/* port number */

struct IN_ADDR sin_addr;//protocol specific address

unsigned char sin_zero[8];/* fill 0*/

}

struct in_addr{

union{

struct{

unsigned char s_b1,s_b2,s_b3,s_b4;

}s_un_b;

struct{

unsigned short s_w1,s_w2;

}s_un_w;

unsigned long s_addr;

}s_un_w;

}IN_ADDR;

Bigendian on the network (low byte first transmission)

Socket programming functions

Socket: Creating sockets

Bind: Used to bind IP address and port number to socket

Connect: This function is used to establish a connection to the server

Listen: Set maximum connection requirements that the server can handle

Accept: waits for a socket connection request from a user Client

Send: Sending data

Recv: Receiving data