Android NDK中socket的用法以及注意事项分析

#include <sys/select.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define max_data_buf_len 10240
int sd = invalid_socket;
sockaddr_in addr_org;  // 发送端地址
sd = socket(af_inet, sock_dgram, ipproto_udp);  // 创建socket
addr_org.sin_family = af_inet;
addr_org.sin_addr.s_addr = inet_addr("192.128.0.1");  // 发送端ip
addr_org.sin_port = htons(8080);  // 发送端端口
bind(sd, (struct sockaddr *)&(addr_org), sizeof(struct sockaddr_in));  // 绑定ip和端口

sockaddr_in addr_dst;  // 接收端地址
addr_dst.sin_family = af_inet;
addr_dst.sin_addr.s_addr = inet_addr("192.128.0.2");  // 接收端ip
addr_dst.sin_port = htons(8080);  // 接收端端口
... // 生成要发送的数据到senddatabuff, 长度为ullen
sendto(sd, senddatabuff, ullen, 0, (struct sockaddr *)&(addr_dst), sizeof(sockaddr_in));  // 发送senddatabuff中的数据

void *socketreceivethread(void *pparam)
{
    fd_set fdset;
    struct timeval delayval;
    unsigned long lretval;
    delayval.tv_sec  = 0;
    delayval.tv_usec = 5000;    /*5ms延时*/
    while (!end_flag)
    {
        fd_zero(&fdset);
        fd_set(sd, &fdset);
        lretval = select(sd+1, &fdset, null, null, &delayval); // 尤其要注意第一个参数
        if (0 == lretval)
        {
            continue;
        }
        else if (socket_error == lretval)
        {
            break;
        }
        else if (fd_isset(sd, &fdset) != 0)
        {
            char recvdatabuff[max_data_buf_len];  // 接收数据buffer
            unsigned long ullen = recvfrom(sd, recvdatabuff, max_data_buf_len, 0, null, null);
            ... // 处理接收到的数据
        }
    }
}