网络编程之排除udp判断客户端是否断开
思路：每几秒发送一条不显示的信息，客户端断开则不再发送信息，超时则表现客户端断开毗连。（心跳包）https://i-blog.csdnimg.cn/direct/b8fc796289794b9d8138e6ec22290208.png
服务器
#include <head.h>
#define MAX_CLIENTS 100// 最大支持100个客户端
#define TIMEOUT 5 // 5秒超时
struct Client {
struct sockaddr_in addr;
time_t last_seen;// 记录最后一次收到该客户端数据的时间
};
struct Client client_list;
int client_count = 0;
// **更新客户端心跳时间**
void update_client(struct sockaddr_in *client_addr) {
time_t now = time(NULL);
for (int i = 0; i < client_count; i++) {
if (memcmp(&client_list.addr, client_addr, sizeof(struct sockaddr_in)) == 0) {
client_list.last_seen = now;// 更新时间
return;
}
}
// **如果客户端不在列表中，则添加**
if (client_count < MAX_CLIENTS) {
client_list.addr = *client_addr;
client_list.last_seen = now;
client_count++;
}
}
// **检查超时客户端**
void check_clients() {
time_t now = time(NULL);
for (int i = 0; i < client_count; i++) {
if (now - client_list.last_seen > TIMEOUT) {
printf("客户端 %s:%d 断开\n",
inet_ntoa(client_list.addr.sin_addr),
ntohs(client_list.addr.sin_port));
// **移除客户端**
for (int j = i; j < client_count - 1; j++) {
client_list = client_list;
}
client_count--;
i--;// **继续检查下一个**
}
}
}
int main(int argc, const char *argv[]) {
if (argc < 2) {
printf("请输入端口号\n");
return 1;
}
short port = atoi(argv);
// **创建 UDP 套接字**
int receiver = socket(AF_INET, SOCK_DGRAM, 0);
struct sockaddr_in addr = {0};
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = inet_addr("0.0.0.0");
if (bind(receiver, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
perror("bind");
return 1;
}
printf("服务器启动，监听端口 %d\n", port);
struct sockaddr_in client_addr;
socklen_t addr_len = sizeof(client_addr);
char buf;
fd_set readfds;
struct timeval timeout;
while (1) {
// **使用 select 进行超时检测**
FD_ZERO(&readfds);
FD_SET(receiver, &readfds);
timeout.tv_sec = 1;// 每秒检查一次
timeout.tv_usec = 0;
int activity = select(receiver + 1, &readfds, NULL, NULL, &timeout);
if (activity > 0) {
// **接收数据**
memset(buf, 0, sizeof(buf));
int len = recvfrom(receiver, buf, sizeof(buf) - 1, 0, (struct sockaddr*)&client_addr, &addr_len);
if (len > 0) {
buf = '\0';
update_client(&client_addr);// **更新心跳时间**
// **如果是心跳包 "PING"，不打印、不转发**
if (strcmp(buf, "PING") == 0) {
continue;
}
printf("收到消息: %s\n", buf);
// **转发消息给所有在线客户端**
for (int i = 0; i < client_count; i++) {
sendto(receiver, buf, strlen(buf), 0,
(struct sockaddr*)&client_list.addr, sizeof(client_list.addr));
}
}
}
// **检查超时客户端**
check_clients();
}
return 0;
}
客户端
#include <head.h>
#include <pthread.h>
#define BUF_SIZE 64
int sender;// 套接字
struct sockaddr_in addr;
void *heartbeat(void* arg)
{
while(1)
{
// 发送空的心跳包
sendto(sender, "", 1, 0, (struct sockaddr*)&addr, sizeof(addr));
sleep(2);// 每2秒发送一次心跳包
}
}
int main(int argc, const char *argv[])
{
if (argc < 2) {
printf("请输入端口号\n");
return 1;
}
short port = atoi(argv);
// 创建套接字
sender = socket(AF_INET, SOCK_DGRAM, 0);
if (sender == -1) {
perror("创建套接字失败");
return 1;
}
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = inet_addr("192.168.128.20");// 服务器的IP地址
// 启动心跳包线程
pthread_t heart;
pthread_create(&heart, NULL, heartbeat, NULL);
while (1) {
char buf = "";
printf("输入：");
scanf("%s", buf);
getchar();// 读取输入并去掉换行符
// 发送普通消息
sendto(sender, buf, strlen(buf), 0, (struct sockaddr*)&addr, sizeof(addr));
// 接收服务器的回复
int len = recvfrom(sender, buf, BUF_SIZE - 1, 0, NULL, NULL);
if (len > 0) {
buf = '\0';// 确保字符串以 '\0' 结尾
printf("接收到回复的消息: %s\n", buf);
} else {
printf("接收服务器消息失败\n");
}
}
// 关闭套接字
close(sender);
return 0;
}
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