[1] >> 提问:网络基础知识?
<√>-->>端口号16位(1-65535) = 常用端口(1~1023) + 不能使用的端口(1024 ~ 5000) + 用户端口( 5000 ~ 65535 )
<√>-->>字节序 = 大端模式 (高字节-->低地址) + 小端模式(低字节-->低地址) #网络字节序，即大端字节序
<√>-->>Internet是“冷战”的产物--阿帕网
<√>-->>TCP / IP层次
[
应用层
表示层
会话层
传输层
网络层
数据链路层
物理层
]
[2] >> socket编程
[
<√>流式套接字SOCK_STREAM： 面向TCP编程,数据被看作是字节流
<√>数据报套接字SOCK_DGRAM：面向UDP编程,数据以独立数据包的形式发送
<√>原始套接字_SOCK_RAW： 穿透TCP/UDP传输层,能在网络层进行编程[raw = 未加工的]
<√>-->>int inet_pton(int af, const char *src, void *dst);[return:-1-->errro]
[
description :
convert IPv4 and IPv6 addresses from text to binary form
This function converts the character string src into a network address structure in the af address family,
then copies the network address structure to dst.
The af argument must be either AF_INET or AF_INET6.
]
<√>-->>convert(转换) values between host and network byte order
[
<√>uint32_t htonl(uint32_t hostlong); #l = long
#The htonl() function converts the unsigned integer(整数) hostlong from host(主机) byte order to network byte order.
<√>uint16_t htons(uint16_t hostshort); #s = short
#The htons() function converts the unsigned short integer hostshort from host byte order to network byte order.
<√>uint32_t ntohl(uint32_t netlong);
#The ntohl() function converts the unsigned integer netlong from network byte order to host byte order.
<√>uint16_t ntohs(uint16_t netshort);
#The ntohs() function converts the unsigned short integer netshort from network byte order to host byte order.
]
]
[3] >> TCP编程?
[
----------------------------------------------------------------------------------
TCP编程流程:
[服务器端] [客户端]
socket socket
↓ |
bind |
↓ |
listen |
↓ ↓
accept <--------- connect
↓ ↓
--------------------------
read write
write read
--------------------------
↓ ↓
close close
----------------------------------------------------------------------------------
struct sockaddr.sin_addr = INADDY_ANY = 动态IP
<√>1>> int socket(int domain, int type, int protocol);
[
DESCRIPTION:
socket() creates an endpoint(末尾节点) for communication and returns a file descriptor that refers to
that endpoint
The domain argument specifies a communication domain(区域)
AF_INET IPv4 Internet protocols
AF_INET6 IPv6 Internet protocols
AF_LOCAL Synonym for AF_UNIX
Currently(一般) defined types are:
SOCK_STREAM
SOCK_DGRAM
SOCK_RAW
protocol(协议):
UDP与TCP编程时写0
On success, a file descriptor for the new socket is returned. On error, -1 is returned
]
<√>2>>int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
[
NAME
bind -- assign a local protocol address to a socket
DESCRIPTION
The bind() system call assigns(分配) the local protocol address to a socket.
When a socket is created with socket() it exists in an address family
space but has no protocol address assigned(指定).
The bind() system call requests that addr be assigned to the socket.
RETURN VALUES
The bind() function returns the value 0 if successful;-1 is error
]
<x>3>>int listen(int socket, int backlog);
[
Name:
listen - listen for socket connections and limit the queue of incoming connections
Description:
The listen() function shall(将会) mark(标记) a connection-mode socket, specified by the socket argument,
as accepting(统一) connections.
backlog = 监听个数
Return Value:
successful completions, listen() shall return 0 , error return -1 ;
]
<√>4>>int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
[
NAME:
accept, - accept a connection on a socket
DESCRIPTION:
The accept() system call is used with connection-based socket types(SOCK_STREAM)
It extracts(提取) the first connection request on the queue of pending connections for the listening socket
sockfd:
The argument sockfd is a socket that has been created with socket(2),
bound to a local address with bind(2), and is listening for
connections after a listen(2).
addr :
The argument addr is a pointer to a sockaddr structure.
addrlen:
The addrlen argument is a value-result argument: the caller must
initialize it to contain the size of the structure pointed to by addr
RETURN VALUE:
On success, these system calls return a new file descriptor for the
accepted socket ,error return -1 ;
]
<√>5>> 读,写,关闭
ssize_t read(int fd, void *buf, size_t count);
ssize_t write(int fd, const void *buf, size_t count);
int close(int fd); [-1-->error ; 0--> success]
<√>6>>int connect(int socket, const struct sockaddr *address, socklen_t address_len); [return:-1-->error;0-->success]
[
Name:
connect - connect a socket
Description
The connect() function shall attempt to make a connection on a socket.
The function takes the following arguments:
socket
Specifies(指定) the file descriptor associated(联系) with the socket.
address
Points to a sockaddr structure containing the peer address.
The length and format(格式) of the address depend on the address family of the socket.
address_len
Specifies the length of the sockaddr structure pointed to by the address argument.
]
]
[4] >>UDP编程
[
-->>UDP编程流程
----------------------------------------------------------------------
[服务器端] [客户端]
socket socket
↓ |
bind |
↓ ↓
recvfrom<--request--sendto
↓ ↓
sendto -response->recvfrom
↓ ↓
close close
----------------------------------------------------------------------
-->>UDP 系统调用接口
[
-->>UDP发送数据没有实际的发送缓冲区，所以UDP协议中不存在发送缓冲区满的情况，永远都不会阻塞。
<√>1>> int socket(int domain, int type, int protocol);
[
DESCRIPTION:
socket() creates an endpoint(末尾节点) for communication and returns a file descriptor that refers to
that endpoint
The domain argument specifies a communication domain(区域)
AF_INET IPv4 Internet protocols
AF_INET6 IPv6 Internet protocols
AF_LOCAL Synonym for AF_UNIX
Currently(一般) defined types are:
SOCK_STREAM
SOCK_DGRAM
SOCK_RAW
protocol(协议):
UDP与TCP编程时写0
On success, a file descriptor for the new socket is returned,error return -1;
]
<√>2>> int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
[
NAME
bind -- assign(分配) a local protocol address to a socket
DESCRIPTION
The bind() system call assigns the local protocol address to a socket.
When a socket is created with socket(2) it exists in an address family
space but has no protocol address assigned. The bind() system call re-
quests that addr be assigned to the socket.
The bind() function returns the value 0 if successful;-1 is error
]
<x>3>>ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,struct sockaddr *src_addr, socklen_t *addrlen);
[
NAME
recv, recvfrom, recvmsg - receive a message from a socket
recvfrom()
recvfrom() places the received message into the buffer buf. The
caller must specify the size of the buffer in len.
flags == 操作方式(一般设置为0)
return:
These calls return the number of bytes received, or -1 if an error occurred.
The return value will be 0 when the peer(盯着) has performed an orderly(有序) shutdown.
]
<x>4>>ssizex_t sendto(int sockfd, const void *buf, size_t len, int flags,const struct sockaddr *dest_addr, socklen_t addrlen);
[
Description
The system calls send(), sendto(), and sendmsg() are used to transmit a message to another socket.
The argument sockfd is the file descriptor of the sending socket.
the message is found in buf and has length len
flags == 操作方式(一般设置为0)
return:
On success, these calls return the number of characters sent. On error, -1 is returned, and
errno is set appropriately.
]
<√>5>> int close(int fd);
]
[5] >> 并发服务器?
<√>-->>并发 = 多个客户端接入
<√>-->>并发服务器 = 并发多进程服务器 + 并发多线程服务器
[6] >> IO多路复用?
[
<√>-->>linux中每个进程默认情况下，最多可以打开2*10=1024个文件，最多有1024个文件描述符
<√>-->>文件描述符
[
1.非负整数
2.从最小可用的数字来分配
3.每个进程启动时默认打开0,1,2三个文件描述符
]
-->>Linux下的4种IO模型
[
<√>阻塞IO
[
当没有从缓冲区读到数据,当前进程就休眠,当缓冲区内有数据后,进程被唤醒,读取缓冲区的数据
例:读操作中的read、 recvfrom
例:写操作中的 write、send
例:socket中的：accept、 connect
]
<√>非阻塞IO
[
1:IO操作不能够立即完成，请马上返回一个错误给我
2:使用了非阻塞模式，需要使用循环不停地测试文件描述符是否可以操作,我们称之为polling
]
<x>复用IO
[
当文件描述符集合有一个描述符准备就绪时,可以进行IO操作;
<x>-->> int select(int nfds, fd_set *readfds, fd_set *writefds,fd_set *exceptfds, struct timeval *timeout);
[
NAME
select - synchronous I/O multiplexing
DESCRIPTION top
select() allows a program to monitor(监听) multiple(许多) file descriptors,
waiting until one or more of the file descriptors become "ready" for
some class of I/O operation (e.g.(例如), input possible).
A file descriptor is considered ready if it is possible to perform a
corresponding I/O operation (e.g., read(2), or a sufficiently small
write(2)) without blocking.
nfds:
This argument should be set to the highest-numbered file descriptor in any of the three sets, plus(加) 1.
readfds:
The file descriptors in this set are watched to see if they are ready for reading
After select() has returned, readfds will be cleared of all
writefds:
The file descriptors in this set are watched to see if they are ready for writing
After select() has returned, writefds will be cleared of all
exceptfds:
The file descriptors in this set are watched for "exceptional(异常) conditions(条件)".
timeout
The timeout argument is a timeval structure (shown below) that
specifies the interval that select() should block waiting for
a file descriptor to become ready. The call will block until
either:
• a file descriptor becomes ready;
• the call is interrupted by a signal handler; or
• the timeout expires.
RETURN VALUE top
On success, select() and pselect() return the number of file
descriptors contained in the three returned descriptor sets (that is,
the total number of bits that are set in readfds, writefds,
exceptfds). -1 is error;
------------------------------------------------------------------------
-->>select()与FD宏的使用流程
socket() socket()
↓ ↓
bind() bind()
↓ ↓
FD_ZERO()
↓ ↓
FD_SET()
↓ ↓
select()
↓ ↓
FD_ISSET()
↓ ↓
recvfrom() sendto() FD_ISSET()
↓ ↓
close() accept()
↓ ↓
FD_CLR()
↓
close()
↓
FD_CLR()
------------------------------------------------------------------------
-->>select种set集合需要用到的参数
<x>void FD_CLR(int fd, fd_set *set);
[
This macro removes the file descriptor fd from set.
]
<x>int FD_ISSET(int fd, fd_set *set);
[
After calling select(), the FD_ISSET()
macro can be used to test if a file descriptor is still
present in a set. FD_ISSET() returns nonzero if the file
descriptor fd is present in set, and zero if it is not.
]
<x>void FD_SET(int fd, fd_set *set);
[
This macro(宏) adds the file descriptor fd to set.
]
<x>void FD_ZERO(fd_set *set);
[
This macro(宏) clears set.
It should be employed(使用) as the first step in initializing a file descriptor set.
]
]
]
信号驱动IO
[
进程要定义一个信号处理程序
]
]
]
[7] >> TCP,IP协议
-->>计算机网络的知识点
-->><<计算机网络一书>>
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