Linux系統udp模式下服務器與客戶端通信（可同時多個客戶端一起通訊）

//ser.c
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>

#include<sys/socket.h>
#include<netinet/in.h>

int main()
{
    int sockSer = socket(AF_INET, SOCK_DGRAM, 0);
    if(sockSer == -1)
    {
        perror("socket");
        exit(1);
    }

    struct sockaddr_in addrSer;
    addrSer.sin_family = AF_INET;
    addrSer.sin_port = htons(8080);//端口號
    addrSer.sin_addr.s_addr = inet_addr("192.168.1.xx");//服務器地址

    socklen_t addrlen = sizeof(struct sockaddr);
    int ret = bind(sockSer, (struct sockaddr*)&addrSer, addrlen);
    if(ret == -1)
    {
        perror("bind.");
        exit(1);
    }

    struct sockaddr_in addrCli;

    char sendbuf[256];
    char recvbuf[256];
    while(1)
    {
        recvfrom(sockSer, recvbuf, 256, 0, (struct sockaddr*)&addrCli, &addrlen);
        printf("Cli:>%s\n", recvbuf);
        printf("Ser:>");
        scanf("%s",sendbuf);
        sendto(sockSer, sendbuf, strlen(sendbuf)+1, 0, (struct sockaddr*)&addrCli, addrlen);
    }

    close(sockSer);
    return 0;
}


//cli.c
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>

#include<sys/socket.h>
#include<netinet/in.h>

int main()
{
    int sockCli = socket(AF_INET, SOCK_DGRAM, 0);
    if(sockCli == -1)
    {
        perror("socket");
        exit(1);
    }

    struct sockaddr_in addrSer;
    addrSer.sin_family = AF_INET;
    addrSer.sin_port = htons(8080);//端口號
    addrSer.sin_addr.s_addr = inet_addr("192.168.1.xx");//服務器地址

    socklen_t addrlen = sizeof(struct sockaddr);

    char sendbuf[256];
    char recvbuf[256];
    while(1)
    {
        printf("Cli:>");
        scanf("%s",sendbuf);
        sendto(sockCli, sendbuf, strlen(sendbuf)+1, 0, (struct sockaddr*)&addrSer, addrlen);

        recvfrom(sockCli, recvbuf, 256, 0, (struct sockaddr*)&addrSer, &addrlen);
        printf("Cli:>%s\n", recvbuf);
    }
    close(sockCli);
    return 0;
}

可實現多個客戶端與服務器通訊，客戶端端口號和地址必須和服務器一樣

但udp模式不像tcp先進行鏈接，所以必須客戶端先發起通訊，讓服務器得到客戶端的地址，才能進行通訊，而且限制每次發送的次數（客戶端一句，服務器一句）還需要改進