First, the emergence of the Internet
In October and November 1957, In 1958, President Eisenhower proposed to the U.S. Congress to establish DARPA (Defense Advanced Research Project Agency). In June 1968, DARPA proposed Resource Sharing Computer Networks to connect DARPA computers. The network was called ARPAnet, or ARPAnet. It was the earliest prototype of InterneCopy the codeTCP is divided into two different protocols:
1. Transmission control protocol TCP used to detect errors in network transmission
2. Internet protocol IP that is specially responsible for interconnecting different networks
Second, network architecture
The OSI model
Three, IP
Basic concepts of IP:
An IP address is the identifier of a host on the Internet
A host address on the Internet must have an IP address to communicate with other machines
The IP address can be 32-bit (IPv4) or 128-bit (IPv6).
Each packet must carry a destination IP address and a source address, and the router relies on this information to route the packet
Representation: The common dotted form, such as 202.35.64.12, is eventually converted to a 32-bit unsigned integer
IP Address Classification
A total of five categories
(1) Class A 1.0.0.1-126.255.255.254 Government and Reserved (2) Class B 128.0.0.1-191.255.255.254 Large and Medium Enterprises (3) Class C 192.0.0.1-223.255.255.254 Common (4) Class D 224.0.0.0-239.255.255.255 multicast (5) Class E 240.0.0.0-255.255.255.254 experimentCopy the code
IP address: 192.168.1.155
Network address + host address
Special IP:
An address (” 0.0.0.0 “) where each byte is 0 corresponds to the current host address: INADDR_ANY
127.0.0.1 to 127.255.255.255 Used for loop testing. For example, 127.0.0.1 can represent the local IP address. You can use http://127.0.0.1 to test the web server configured on the local server
The IP address where each bit of the host address is 1 is the broadcast address of the current subnet
An IP address in which each bit of the network part is 1 and each bit of the host part is 0 is a subnet mask
In the IP address, the host part is 1, xxx.XXX.XXX.1 this is the gateway address, router address
Subnet mask:
255.255.255.0 This is the address of the subnet mask (class C).
An address in which all the network parts are ones and all the host parts are zeros is a subnet mask
Port number:
To further distinguish which process a host should forward packets to for processing, use the port number
(1) 1-1023 (Ports 1-255 are well-known ports, and ports 256 to 1023 are usually occupied by UNIX systems)
(2) Registered port: 1024 to 49150
(3) Dynamic or private port: 49151 to 65535
Byte order:
Data transmitted on the network must be in network byte order: big endian
The socket socket
7 file types – D, P, C, B, L, S
Six interprocess communication modes pipes, shared memory, semaphores, signals, message queues, sockets
Process communication interface, special file descriptor
Socket classification
(1) Stream socket (TCP socket) (SOCK_STREAM)
Provides a connection-oriented, reliable data transfer service that sends data error-free, duplicate-free and receives data in the order it is sent. Set the flow control to prevent the data flow from drowning the slow receiver. Data is treated as a byte stream with no length limitation.Copy the code(2) Datagram socket (UDP socket) (SOCK_DGRAM)
Provides connectionless service. Data packets are sent as independent packets without error assurance. Data may be lost or repeated. Data may be sent sequentially or received out of order.Copy the code(3) Raw socket (SOCK_RAW)
It can directly access lower-level protocols such as IP and ICMP.Copy the code
Socket programming often has an API
TCP and UDP communication are related
Socket () creates a socket
Bind () binds the local address and port
Connect () establishes a connection
Listen () Sets the listening port
Accept () accepts the TCP connection
Recv (), read(), recvfrom() Data received
Send (), write(), sendto() Data is sent
Close (), shutdown() closes the socket
Network address translation function
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
int inet_aton(const char *cp, struct in_addr *inp);
in_addr_t inet_addr(const char *cp);
in_addr_t inet_network(const char *cp);
char *inet_ntoa(struct in_addr in);
struct in_addr inet_makeaddr(in_addr_t net, in_addr_t host);
in_addr_t inet_lnaof(struct in_addr in);
in_addr_t inet_netof(struct in_addr in);
Copy the codeGets and sets socket properties
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int getsockopt(int sockfd, int level, int optname,
void *optval, socklen_t *optlen);
int setsockopt(int sockfd, int level, int optname,
const void *optval, socklen_t optlen);
#include <arpa/inet.h>
uint32_t htonl(uint32_t hostlong);
Copy the codeHost byte order is converted to unsigned long integer network byte order
uint16_t htons(uint16_t hostshort);
Copy the codeHost byte order is converted to unsigned short integer network byte order
uint32_t ntohl(uint32_t netlong);
uint16_t ntohs(uint16_t netshort);
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