[网络协议]UDP编程

UDP编程

本文内容来源于《TCP/IP网络编程第六章》。主要需要了解UDP常用两个函数：sendto()和recvfrom(),其中两个函数调用次数要相同，如下面例子所示：
server端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30
void error_handling(char * message);

int main(int argc,char *argv[]){
    int sock;
    char message[BUF_SIZE];
    int str_len,i;
    socklen_t adr_sz;

    struct sockaddr_in my_adr,your_adr;
    if(argc!=2){
        printf("usage : %s <port>\n",argv[0]);
        exit(1);
    }
    sock = socket(PF_INET,SOCK_DGRAM,0);
    if(sock == -1)
     error_handling("UDP socket creation error");
			        
    memset(&my_adr,0,sizeof(my_adr));
    my_adr.sin_family = AF_INET;
    my_adr.sin_addr.s_addr=htonl(INADDR_ANY);
    my_adr.sin_port=htons(atoi(argv[1]));		
    if(bind(sock,(struct sockaddr*)&my_adr,sizeof(my_adr))==-1)
           error_handling("bind() error");
    for(i=0;i<3;i++){
        sleep(5);
	adr_sz = sizeof(your_adr);
	str_len=recvfrom(sock,message,BUF_SIZE,0,(struct sockaddr*)&your_adr,&adr_sz);
	printf("message %d: %s\n",i+1,message);
	}
      close(sock);
      return 0;
 }

void error_handling(char *message){
    fputs(message,stderr);
    fputc('\n',stderr);
    exit(1);
}

客户端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30
void error_handling(char * message);

int main(int argc,char *argv[]){
    int sock;
    char msg1[] = "Hi!";
    char msg2[]="I 'm zzy";
    char msg3[] = "Nicw to meet you";

    socklen_t your_adr_sz;

    struct sockaddr_in your_adr;
    if(argc!=3){
        printf("usage : %s <port>\n",argv[0]);
        exit(1);
    }

    sock = socket(PF_INET,SOCK_DGRAM,0);
    if(sock == -1)
        error_handling("socket() error");
    
    memset(&your_adr,0,sizeof(your_adr));
    your_adr.sin_family = AF_INET;
    your_adr.sin_addr.s_addr=inet_addr(argv[1]);
    your_adr.sin_port=htons(atoi(argv[2]));

    sendto(sock,msg1,sizeof(msg1),0,(struct sockaddr*)&your_adr,sizeof(your_adr));
    sendto(sock,msg2,sizeof(msg2),0,(struct sockaddr*)&your_adr,sizeof(your_adr));
    sendto(sock,msg3,sizeof(msg3),0,(struct sockaddr*)&your_adr,sizeof(your_adr));
    close(sock);
    return 0;
}

void error_handling(char *message){
    fputs(message,stderr);
    fputc('\n',stderr);
    exit(1);
}