Linux下C語言實現UDP Socket編程

該博文參考了Linux C socket 編程之UDP一文，在這裏表示感謝！

發送方：

/* 
 * File:   udp_sender.c
 * Author: Henry
 *
 * Created on 2019年5月29日17:08:13
 *
 * 主要實現：發送20個文本消息，然後再發送一個終止消息
 */
 
#include <stdio.h>
#include <stdlib.h>
 
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

int power(int base, int exp);
int str_to_num(const char *s);

int main(int argc, char** argv) {
	if(argc != 3)
	{
		printf("Warning: Incorrect parameters! Correct usage like this:\nudp_sender ipAddress_of_udpServer port\n");
		exit(0);
	}
    int socket_descriptor; //套接口描述字
    int iter=0;
    char buf[80];
    struct sockaddr_in address;//處理網絡通信的地址
 
    bzero(&address,sizeof(address));
    address.sin_family=AF_INET;
    //address.sin_addr.s_addr=inet_addr("192.168.2.1");//這裏不一樣
    address.sin_addr.s_addr=inet_addr(argv[1]);//這裏不一樣
    address.sin_port=htons(str_to_num(argv[2]));
 
    //創建一個 UDP socket
 
    socket_descriptor=socket(AF_INET,SOCK_DGRAM,0);//IPV4  SOCK_DGRAM 數據報套接字（UDP協議）
 
    for(iter=0;iter<=20;iter++)
    {
         /*
         * sprintf(s, "%8d%8d", 123, 4567); //產生：" 123 4567" 
         * 將格式化後的字符串存放到s當中
         */
        sprintf(buf,"data packet with ID %d\n",iter);
       
        /*int PASCAL FAR sendto( SOCKET s, const char FAR* buf, int len, int flags,const struct sockaddr FAR* to, int tolen);　　
         * s：一個標識套接口的描述字。　
         * buf：包含待發送數據的緩衝區。　　
         * len：buf緩衝區中數據的長度。　
         * flags：調用方式標誌位。　　
         * to：（可選）指針，指向目的套接口的地址。　
         * tolen：to所指地址的長度。  
　　      */
        sendto(socket_descriptor,buf,sizeof(buf),0,(struct sockaddr *)&address,sizeof(address));
    }
 
    sprintf(buf,"stop\n");
    sendto(socket_descriptor,buf,sizeof(buf),0,(struct sockaddr *)&address,sizeof(address));//發送stop 命令
    close(socket_descriptor);
    printf("Messages Sent,terminating\n");
 
    exit(0);
 
    return (EXIT_SUCCESS);
}

int str_to_num(const char* s)
{
	int exp=0, n=0;
	const char *h = s;
	const char *t = NULL;
	for(;*h <'0' || *h >'9'; h++)  // 找到第一位數字
		;
	for(t=h; *t >='0' && *t <='9'; ++t)  // 找到最後一位數字
		;
	t--;
	while(t >= h)
	{
		n += (*t - 48)*power(10, exp);
		t--;
		exp++;
	}
	return n;
}

int power(int base, int exp)
{
	if( 0 == exp )
		return 1;
	return base*power(base, exp-1);
}

接收方：

/* 
 * File:   udp_receiver.c
 * Author: Henry
 *
 * Created on 2019年5月29日17:09:11
 *
 * 主要實現：發送20個文本消息，然後再發送一個終止消息
 */
 
#include <stdio.h>
#include <stdlib.h>
 
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

int power(int base, int exp);
int str_to_num(const char *s);
 
int main(int argc, char** argv) {
	if(argc != 2)
	{
		printf("Warning: Incorrect parameters! Correct usage like this:\nudp_receiver port\n");
		exit(0);
	}
 
    int sin_len;
    char message[256];
 
    int socket_descriptor;
    struct sockaddr_in sin;
    printf("Waiting for data from sender \n");
 
    bzero(&sin,sizeof(sin));
    sin.sin_family=AF_INET;
    sin.sin_addr.s_addr=htonl(INADDR_ANY);
    sin.sin_port=htons(str_to_num(argv[1]));
    sin_len=sizeof(sin);
 
    socket_descriptor=socket(AF_INET,SOCK_DGRAM,0);
    bind(socket_descriptor,(struct sockaddr *)&sin,sizeof(sin));
 
    while(1)
    {
        recvfrom(socket_descriptor,message,sizeof(message),0,(struct sockaddr *)&sin,&sin_len);
        printf("Response from server:%s\n",message);
        if(strncmp(message,"stop",4) == 0)     // 接受到的消息爲 “stop”
        {
 
            printf("Sender has told me to end the connection.\n");
            break;
        }
    }
 
    close(socket_descriptor);
    exit(0);
 
    return (EXIT_SUCCESS);
}

int str_to_num(const char* s)
{
	int exp=0, n=0;
	const char *h = s;
	const char *t = NULL;
	for(;*h <'0' || *h >'9'; h++)  // 找到第一位數字
		;
	for(t=h; *t >='0' && *t <='9'; ++t)  // 找到最後一位數字
		;
	t--;
	while(t >= h)
	{
		n += (*t - 48)*power(10, exp);
		t--;
		exp++;
	}
    	return n;
}

int power(int base, int exp)
{
	if( 0 == exp )
		return 1;
	return base*power(base, exp-1);
}