怎么设置tcp_keepalive设置

在Linux系统中，可以使用`setsockopt`函数来设置TCP Keepalive参数。具体步骤如下：

1. 创建一个socket连接

int sockfd = socket(AF_INET, SOCK_STREAM, 0);

2. 设置keepalive参数

int keepAlive = 1; // 开启keepalive
int keepIdle = 60; // 如该连接在60秒内没有任何数据往来,则进行探测
int keepInterval = 5; // 探测时发包的时间间隔为5 秒
int keepCount = 3; // 探测尝试的次数.如果第1次探测包就收到响应了,则后2次的不再发送
setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, (void *)&keepAlive, sizeof(keepAlive));
setsockopt(sockfd, SOL_TCP, TCP_KEEPIDLE, (void*)&keepIdle, sizeof(keepIdle));
setsockopt(sockfd, SOL_TCP, TCP_KEEPINTVL, (void *)&keepInterval, sizeof(keepInterval));
setsockopt(sockfd, SOL_TCP, TCP_KEEPCNT, (void *)&keepCount, sizeof(keepCount));

3. 连接服务器

struct sockaddr_in servaddr;
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(port);
inet_pton(AF_INET, ip, &servaddr.sin_addr);
connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

4. 发送和接收数据

char sendbuf[1024];
char recvbuf[1024];
while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL) {
    write(sockfd, sendbuf, strlen(sendbuf));
    int n = read(sockfd, recvbuf, sizeof(recvbuf));
    if (n < 0) {
        printf("read error\n");
        break;
    }
    recvbuf[n] = 0;
    fputs(recvbuf, stdout);
}

5. 关闭socket连接

close(sockfd);