简单的udp客户服务端程序

服务端程序：server.c

#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdio.h>




#define PORT 12345

int main()
{
        struct sockaddr_in server_addr, client_addr;
        char msg[1024];
        int len;
        static count = 1;
        int fd = socket(AF_INET, SOCK_DGRAM, 0);
        bzero(&server_addr, sizeof(struct sockaddr_in));

        server_addr.sin_family = AF_INET;
        server_addr.sin_port = htons(PORT);
        server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

        bind(fd, (struct sockaddr*)&server_addr, sizeof(struct sockaddr_in));

        socklen_t addr_len;
        while(1)
        {
                bzero(msg, sizeof(msg));
                                addr_len = sizeof(client_addr);
                len = recvfrom(fd, msg, sizeof(msg), 0, (struct sockaddr*)&client_addr, &addr_len);//百度百科直接搜
                printf("%d: ", len);
                printf("msg from: %s
", inet_ntoa(client_addr.sin_addr));
                printf("msg: %s
", msg);
                sendto(fd, msg, len, 0, (struct sockaddr*)&client_addr, addr_len);//百度百科直接搜

        }

        return 0;

}

客户端程序：client.c

#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdio.h>




#define PORT 12345 
#define IP "127.0.0.1"
int main()
{
    struct sockaddr_in server_addr;
    char msg[1024];
    int len;
    int fd = socket(AF_INET, SOCK_DGRAM, 0); //创建socket，注意udp创建的是数据包套接字，SOCK_DGRAM
    if(fd < 0)
    {
        printf("socket error
");
    }
    bzero(&server_addr, sizeof(struct sockaddr_in)); //相当于memset(&server_addr, 0, sizeof(struct sockaddr_in));
    
    //指定服务端的端口和ip
    server_addr.sin_family = AF_INET; 
    server_addr.sin_port = htons(PORT);

    inet_pton(AF_INET, "127.0.0.1", &server_addr.sin_addr);
    
    
    socklen_t addr_len;
    int ret;
    int n;
    while(1)
    {
        //int n = read(STDIN_FILENO, msg, sizeof(msg));
        fgets(msg, 1024, stdin); //用户输入字符串，fgets会读入字符'
'
        printf(" msg: %s",  msg);
        //发送到server端
        ret = sendto(fd, msg, strlen(msg), 0, (struct sockaddr*)&server_addr, sizeof(server_addr));
        printf("ret: %d
", ret);
        //接收从服务端收到的字符串
        n = recvfrom(fd, msg, sizeof(msg), 0, NULL, NULL);
        printf("n=%d
", n);
        msg[n]='';// 收到的字符串后面没有''，无法printf输出，所以在字符串后添加''
        printf("%s", msg);
        printf("__________________________________
");
        
    }
    
    return 0;
    
}