- UDP server
#include <stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<string.h>
#include<netinet/in.h>
#include<stdlib.h>
void service(int sock){
char buf[128];
struct sockaddr_in client;
socklen_t len=sizeof(client);
while(1){
ssize_t s = recvfrom(sock,buf,sizeof(buf)-1,0,(struct sockaddr*)&client,&len);
if(s > 0){
buf[s]=0;
printf("[%s:%d]:%s\n",inet_ntoa(client.sin_addr));
}
}
}
int main(int argc,char* argv[]){
if(argc != 3){
printf("Usage:%s [ip] [port]\n",argv[0]);
return 3;
}
int sock = socket (AF_INET, SOCK_DGRAM, 0);
if(sock < 0){
perror("socket");
return 1;
}
struct sockaddr_in local;
local.sin_family = AF_INET;
local.sin_port = htons(atoi(argv[2]));
local.sin_addr.s_addr = inet_addr(argv[1]);
if(bind(sock,(struct sockaddr*)&local,sizeof(local)) < 0){
perror("bind");
return 2;
}
service(sock);
}
- UDP client
#include <stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<stdlib.h>
#include<string.h>
int main(int argc,char* argv[]){
if(argc != 3){
printf("Usage:%s [ip] [port]\n",argv[0]);
return 3;
}
int sock = socket (AF_INET, SOCK_DGRAM, 0);
if(sock < 0){
perror("socket");
return 2;
}
struct sockaddr_in server;
server.sin_family = AF_INET;
server.sin_port = htons(atoi(argv[2]));
server.sin_addr.s_addr = inet_addr(argv[1]);
char buf[128];
struct sockaddr_in peer;
socklen_t len = sizeof(peer);
while(1){
buf[0] = 0;
ssize_t s = read(0,buf,sizeof(buf)-1);
if(s > 0){
buf[s-1] = 0;
sendto(sock,buf,strlen(buf),0,(struct sockaddr*)&server,sizeof(server));
ssize_t _s = recvfrom(sock,buf,sizeof(buf)-1,0,(struct sockaddr*)&peer,&len);
if(_s > 0){
buf[_s] = 0;
printf("server echo# %s\n",buf);
}
}
}
}
- Introduction to Correlation Functions
1.socket function
Function: used to create a socket capable of network communication.
Related parameters:
domain: Specifies the protocol family of the communication protocol used by the application. Usually PF_INET/AF_INET, which means the Internet protocol suite (TCP/IP protocol suite).
type: Specifies the type of socket to create. The stream socket type is SOCK_STREAM; the datagram socket type is SOCK_DGEAM.
Protocol: Specifies the communication protocol used by the application, usually 0.
Return value: The descriptor of the newly created socket is returned on success; -1 is returned on failure.
2. bind function
Function: When a Socket is created, there is a default IP address and a default port number in the socket data structure. A service program must call the bind function to bind it with an IP address and a specific port number.
Related parameters:
sockfd: Specifies the socket descriptor to be bound.
addr: Specify a sockaddr structure. The structure definition has been introduced in the blog of network programming socket (2), and will not be repeated here.
addrlen: The size of the structure.
Return value: 0 for success; -1 for failure.
3. recvfrom function
Function: Receive a datagram and save the source address.
Related parameters:
sockfd: A description word representing a connected socket.
buf: Receive data buffer.
len: Buffer length.
flags: call operation mode, usually 0.
src_addr: Points to the buffer containing the source address.
addrlen: Points to the length value of the buffer.
Return value: Returns the number of bytes read on success; returns -1 on failure.
4.sendto function
Function: Send data to the other host from the specified socket.
Related parameters:
sockfd: Index the socket from which data will be sent.
buf: Points to the buffer where the data will be sent.
len: The buffer length of the data to be sent.
flags: call operation mode, usually 0.
dest_addr: Points to the area where the address of the receiver is stored.
addrlen: Points to the length value of the area where the address of the receiver is stored.
Return value: Returns the actual number of characters sent on success; returns -1 on failure.