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Socket socket programming
2022-07-07 11:08:00 【Exy-】
Catalog
common socket API
// establish socket File descriptor (TCP/UDP, client + The server )
int socket(int domain, int type, int protocol);
// Binding port number (TCP/UDP, The server )
int bind(int socket, const struct sockaddr *address,socklen_t address_len);
// Start listening socket (TCP, The server )
int listen(int socket, int backlog);
// Receiving request (TCP, The server )
int accept(int socket, struct sockaddr* address,socklen_t* address_len);
// Establishing a connection (TCP, client )
int connect(int sockfd, const struct sockaddr *addr,socklen_t addrlen);sockaddr structure
socket API It is an abstract network programming interface , It is suitable for various underlying network protocols , Such as IPv4、IPv6. However , Different network protocols have different address formats
- IPv4 and IPv6 The address format of is defined in netinet/in.h in ,IPv4 Address use sockaddr_in The structure represents , Include 16 Bit address type , 16 Bit port number and 32 position IP Address .
- IPv4、IPv6 Address types are defined as constants AF_INET、AF_INET6. such , Just get something sockaddr The first address of the structure , You don't need to know what kind of sockaddr Structure , You can determine the content of the structure according to the address type field .
- socket API You can use it all struct sockaddr * Type said , It needs to be converted into sockaddr_in; That's good This is the universality of the program , You can receive IPv4, IPv6, as well as UNIX Domain Socket All kinds of sockaddr Structure pointer as a parameter ;
although socket api The interface of is sockaddr, But we're really based on IPv4 When programming , The data structure used is sockaddr_in; In this structure, the main There should be three parts of information : Address type , Port number , IP Address .
encapsulation UDPSocket
//udpsocket.cpp
#include<cstdio>
#include<unistd.h>
#include<iostream>
#include<string.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<sys/socket.h>
using namespace std;
class UdpSocket
{
public:
UdpSocket()
:_sockfd(-1)
{}
bool Socket(){
_sockfd=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
if(_sockfd<0)
{
perror("socket error");
return false;
}
return true;
}
bool Bind(const std::string &ip,int port)
{
struct sockaddr_in addr;
addr.sin_family=AF_INET;
addr.sin_port=htons(port);
addr.sin_addr.s_addr=inet_addr(ip.c_str());
socklen_t len=sizeof(struct sockaddr_in);
if(bind(_sockfd,(struct sockaddr*)&addr,len)<0)
{
perror("bind error");
return false;
}
return true;
}
bool Send(const std::string &data,const std::string &ip,int port)
{
struct sockaddr_in peeraddr;
peeraddr.sin_family=AF_INET;
peeraddr.sin_port=htons(port);
peeraddr.sin_addr.s_addr=inet_addr(ip.c_str());
socklen_t len=sizeof(struct sockaddr_in);
int ret=sendto(_sockfd,&data[0],data.size(),0,(struct sockaddr*)&peeraddr,len);
if(ret<0)
{
perror("sendto error");
return false;
}
return true;
}
bool Recv(std::string *buf,std::string *ip=NULL,int *port=NULL)
{
struct sockaddr_in peeraddr;
socklen_t len=sizeof(struct sockaddr_in);
char tmp[4096]={0};
int ret=recvfrom(_sockfd,tmp,4095,0,(struct sockaddr*)&peeraddr,&len);
if(ret<0)
{
perror("recvfrom error");
return false;
}
buf->assign(tmp,ret);
if(ip!=NULL)
*ip=inet_ntoa(peeraddr.sin_addr);
if(port!=NULL)
*port=ntohs(peeraddr.sin_port);
return true;
}
bool Close()
{
if(_sockfd>0)
{
close(_sockfd);
_sockfd=-1;
}
return true;
}
private:
int _sockfd;
};
udp Client code
#include<iostream>
#include<cstdlib>
#include"udpsocket.cpp"
#include<string.h>
#define CHECK_RET(q) if((q)==false){return -1;}
using namespace std;
int main(int argc,char*argv[])
{
if(argc<3)
{
cout<<"usage: Please enter the server address information !\n";
cout<<"\t./udp_client 192.168.1.2 9000\n";
return -1;
}
string srv_ip=argv[1];
int srv_port=atoi(argv[2]);
UdpSocket sock;
CHECK_RET(sock.Socket());
while(1)
{
string buf;
cout<<"client input";
cin>>buf;
CHECK_RET(sock.Send(buf,srv_ip,srv_port));
buf.clear();
CHECK_RET(sock.Recv(&buf));
cout<<"sever response: "<<buf<<endl;
}
sock.Close();
return 0;
}
udp Server code
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<string.h>
int main(int argc,char*argv[])
{
if(argc<3)
{
printf("usage: ./udp_srv 192.168.1.2 9000\n");
return -1;
}
char* srv_ip=argv[1];
int srv_port=atoi(argv[2]);
int sockfd=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
if(sockfd<0)
{
perror("socket error");
return -1;
}
struct sockaddr_in addr;
addr.sin_family=AF_INET;
addr.sin_port=htons(srv_port);
addr.sin_addr.s_addr=inet_addr(srv_ip);
socklen_t len=sizeof(addr);
int ret=bind(sockfd,(struct sockaddr*)&addr,len);
if(ret<0)
{
close(sockfd);
perror("bind error");
return -1;
}
//3. receive data , Receive the peer address
while(1){
char buf[4096]={0};
struct sockaddr_in client_addr;
len=sizeof(client_addr);
ret=recvfrom(sockfd,buf,4095,0,(struct sockaddr*)&client_addr,&len);
if(ret<0)
{
close(sockfd);
perror("recvfrom error");
return -1;
}
printf("%s:%d - %s\n",inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port),buf);
printf("server input");
fflush(stdout);
memset(buf,0x00,4096);
scanf("%s",buf);
ret=sendto(sockfd,buf,strlen(buf),0,(struct sockaddr*)&client_addr,len);
if(ret<0)
{
close(sockfd);
perror("sendto error");
return -1;
}
}
close(sockfd);
return 0;
}
sockaddr_in Members of the struct in_addr sin_addr Express 32 position Of IP Address
But we usually use dotted decimal strings to represent IP Address , The following functions can be represented in a string and in_addr Conversion between representations ;
String rotation in_addr Function of
in_addr Functions that convert strings
among inet_pton and inet_ntop Not only can it be converted IPv4 Of in_addr, You can also convert IPv6 Of in6_addr, So the function interface is void *addrptr.
encapsulation TCPSocket
#include<cstdio>
#include<iostream>
#include<stdlib.h>
#include<unistd.h>
#include<string>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<sys/socket.h>
#include<stdio.h>
#define MAX_LISTEN 5
#define CHECK_RET(q) if((q)==false){return -1;}
class TcpSocket
{
public:
TcpSocket()
:_sockfd(-1)
{}
bool Socket()
{
_sockfd=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(_sockfd<0)
{
perror("socket error");
return false;
}
return true;
}
bool Bind(const std::string&ip,int port)
{
struct sockaddr_in addr;
addr.sin_family=AF_INET;
addr.sin_port=htons(port);
addr.sin_addr.s_addr=inet_addr(ip.c_str());
socklen_t len=sizeof(addr);
if(bind(_sockfd,(struct sockaddr*)&addr,len)<0)
{
perror("bind error");
return false;
}
return true;
}
bool Listen(int backlog=MAX_LISTEN)
{
if(listen(_sockfd,backlog)<0)
{
perror("listen error");
return false;
}
return true;
}
bool Connect(const std::string &srv_ip,int srv_port)
{
struct sockaddr_in addr;
addr.sin_family=AF_INET;
addr.sin_port=htons(srv_port);
addr.sin_addr.s_addr=inet_addr(srv_ip.c_str());
socklen_t len=sizeof(addr);
if(connect(_sockfd,(struct sockaddr*)&addr,len)<0)
{
perror("connect error");
return false;
}
return false;
}
bool Accept(TcpSocket *new_sock,std::string *cli_ip,int *cli_port)
{
struct sockaddr_in addr;
socklen_t len=sizeof(addr);
int newfd=accept(_sockfd,(struct sockaddr*)&addr,&len);
if(newfd<0)
{
perror("accept error");
return false;
}
std::cout<<"new connect:"<<inet_ntoa(addr.sin_addr)<<":"<<ntohs(addr.sin_port)<<"\n";
new_sock->_sockfd=newfd;
if(cli_ip!=NULL)
{
*cli_ip=inet_ntoa(addr.sin_addr);
}
if(cli_port!=NULL)
{
*cli_port=ntohs(addr.sin_port);
}
return true;
}
bool Send(const std::string &data)
{
ssize_t ret=send(_sockfd,data.c_str(),data.size(),0);
{
if(ret<0)
{
perror("send error");
return false;
}
return true;
}
}
bool Recv(std::string *buf)
{
char tmp[4096]={0};
ssize_t ret=recv(_sockfd,tmp,4096,0);
if(ret<0)
{
perror("recv error");
return false;
}
else if(ret==0)
{
std::cout<<"perr shutdown!\n";
return false;
}
buf->assign(tmp,ret);// from tmp Intercept data of specified length , Prevent the end of string mark in the data ;
return true;
}
bool Close()
{
if(_sockfd>0)
{
close(_sockfd);
_sockfd=-1;
}
return true;
}
private:
int _sockfd;
};
tcp Server side
#include"tcp_socket.cpp"
int main(int argc,char *argv[])
{
if(argc<2)
{
std::cout<<"usage: ./tcp_srv 9000\n";
return -1;
}
int port = std::stoi(argv[1]);
// Create socket
TcpSocket lst_sock;
CHECK_RET(lst_sock.Socket());
// Binding address information
CHECK_RET(lst_sock.Bind("0.0.0.0",port));
// Start listening
CHECK_RET(lst_sock.Listen());
while(1)
{
TcpSocket new_sock;
std::string cli_ip;
int cli_port;
CHECK_RET(lst_sock.Accept(&new_sock,&cli_ip,&cli_port));
std::cout<<"new connect: "<<cli_ip<<":"<<cli_port<<"\n";
std::string buf;
new_sock.Recv(&buf);// Communicate with the specified client by creating a new connection
std::cout<<"client say: "<<buf<<std::endl;
buf.clear();
std::cout<<"server say: ";
std::cin>>buf;
new_sock.Send(buf);
}
lst_sock.Close();
return 0;
}
tcp client
#include"tcp_socket.cpp"
int main(int argc,char*argv[])
{
// Although the client does not actively bind addresses , But you must know the address of the server ;
if(argc<3)
{
std::cout<<"usage: arg error\n";
std::cout<<"\t ./tcp_cli 192.168.2.2 9000\n";
return -1;
}
int srv_port=std::stoi(argv[2]);
std::string srv_ip=argv[1];
TcpSocket sock;
// Create socket
CHECK_RET(sock.Socket());
// Send a connection request to the server
CHECK_RET(sock.Connect(srv_ip,srv_port));
while(1)
{
std::string data;
std::cout<<"client say:";
fflush(stdout);
std::cin>>data;
sock.Send(data);
CHECK_RET(sock.Send(data));
data.clear();
CHECK_RET(sock.Recv(&data));
std::cout<<"server say:"<< data<<std::endl;
}
// Close socket
sock.Close();
}
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