linux c 网络，获取本地可用的端口号，判断网络是否连通

矫情吗；* 2022-05-15 01:49 480阅读 0赞

//
    // Created by darren on 18-8-22.
    //
    
    #include <netdb.h>
    #include <errno.h>
    #include <string.h>
    #include <arpa/inet.h>
    #include <fcntl.h>
    #include <unistd.h>
    
    
    int getLocalPort() {
        unsigned short port = 0;
        int sock = socket(AF_INET, SOCK_STREAM, 0);
        if (sock < 0) return port;
        struct sockaddr_in addr;
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = htonl(INADDR_ANY);
        addr.sin_port = 0;        // 若port指定为0,则调用bind时，系统会为其指定一个可用的端口号
        int ret = bind(sock, (struct sockaddr *) &addr, sizeof addr);    // 3. 绑定
        do {
            if (0 != ret) {// 4. 利用getsockname获取
                //LOGE("upn bind, %d, %s", errno, strerror(errno))
                break;
            }
            struct sockaddr_in sockaddr;
            int len = sizeof(sockaddr);
            ret = getsockname(sock, (struct sockaddr *) &sockaddr, (socklen_t *) &len); // this function now not be hooked
    
            if (0 != ret) {
               // LOGE("upn, getsockname:%d, %s", errno, strerror(errno))
                break;
            }
            port = ntohs(sockaddr.sin_port); // 获取端口号
        } while (false);
        //LOGD("UpnConfig::port::%d", port)
        close(sock);
    
        return port;
    }
    
    int getConnectState(int port, const char *ip, int tv_sec, int tv_usec) {
        int fd = -1;
        int ret = 0;
        do {
            fd = socket(AF_INET, SOCK_STREAM, 0);
            if (fd < 0) {
                //LOGE("Test::connect:socket: %d, %s", errno, strerror(errno));
                break;
            }
            struct sockaddr_in addr;
            bzero(&addr, sizeof(addr));
            addr.sin_family = AF_INET;
            addr.sin_port = htons(port);
            addr.sin_addr.s_addr = inet_addr(ip);
    
            int flags = fcntl(fd, F_GETFL, 0);
            if (flags < 0) {
                //LOGE("Test::connect:get flags: %d, %s", errno, strerror(errno));
                break;
            }
            flags |= O_NONBLOCK;
            if (fcntl(fd, F_SETFL, (void *) flags) < 0) {
                // LOGE("Test::connect:set flags: %d, %s", errno, strerror(errno));
                break;
            }
            if (0 == connect(fd, (struct sockaddr *) &addr, sizeof(addr))) {
                break;
            }
            //LOGE("Test::connect:failed: %d, %s", errno, strerror(errno));
    #ifdef __ENABLE_LOG_D__
            if (EINPROGRESS != errno) {
                LOGE("Test::connect:failed: %d, %s", errno, strerror(errno));
                break;
            }
    #endif
            fd_set fdr, fdw;
            FD_ZERO(&fdr);
            FD_ZERO(&fdw);
            FD_SET(fd, &fdr);
            FD_SET(fd, &fdw);
    
            struct timeval timeout;
            timeout.tv_sec = tv_sec;// seconds
            timeout.tv_usec = tv_usec;
            int rc = select(fd + 1, &fdr, &fdw, NULL, &timeout);
            if (0 < rc && (FD_ISSET(fd, &fdw) || FD_ISSET(fd, &fdr))) {
                break;
            }
            if (rc < 0) {
                //LOGE("Test::connect:select: %d, %d, %s", rc, errno, strerror(errno));
                break;
            }
            if (0 == rc) {
                //LOGE("Test::connect:time out: %d, %s", errno, strerror(errno));
                break;
            }
        } while (false);
        if (0 <= fd) {
            close(fd);
        }
        return ret;
    }