通过JNI结合插座

Question

我尝试通过JNI在Linux计算机上打开插座连接。 如果我将java_socket_socket和java_socket_bind组合在同一C函数中，则JNI调用可以很好地工作，但是当我顺序运行方法时，它不起作用。

这是我的代码

#include <jni.h>        // JNI header provided by JDK
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <fcntl.h>
#include "Socket.h"   // Generated

JNIEXPORT jint JNICALL Java_Socket_socket(JNIEnv *env, jobject thisObj) {
    int sockfd;

    if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
        printf("socket creation failed...\n");
        return (jint)-1;
    } else {
        printf("Socket successfully created..\n");
        printf("Socket descriptor: %d\n", sockfd);
        return (jint) sockfd;
    }
}

JNIEXPORT jint JNICALL Java_Socket_bind(JNIEnv *env, jobject thisObj, jint sockfd, jint port) {
    struct sockaddr_in servaddr;
    bzero(&servaddr, sizeof(servaddr));

    int c_sockfd = (int) sockfd;
    short int c_port = (int) port;

    printf("socket binding sockfd - %d, port - %d\n", c_sockfd, c_port);

    // assign IP, PORT
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(c_port);
    printf("htons - %d\n", htons(c_port));


    int one = 1;
    int res = setsockopt(c_sockfd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
    res = setsockopt(c_sockfd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
    if (res < 0) {
        perror("setsockopt");
    }

    printf("sizeof - %d\n", sizeof(servaddr));

    if (fcntl(c_sockfd, F_GETFD) != -1 || errno != EBADF) {
        printf("fd is valid\n");
    } else {
        printf("fd is invalid\n");
    }

    // Binding newly created socket to given IP and verification
    if ((bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr))) != 0) {
        printf("socket bind failed...\n");
        printf("Error code: %d\n", errno);
        return (jint)-1;
    }
    else {
        printf("Socket successfully binded..\n");
        return (jint)0;
    }
}

Java代码

public class Socket {
    static {
        System.load(".../libsocket.so");
    }

    private native int socket();

    private native int bind(int sockFd, int port);

    public static void main(String[] args) {
        var socket = new Socket();
        int sockFd = socket.socket();
        System.out.println("sockFd " + sockFd);
        int bind = socket.bind(sockFd, 9900);
        System.out.println("Bind " + bind);
    }
}

输出：

Socket descriptor: 4
socket binding sockfd - 4, port - 9900
htons - 44070
sizeof - 16
fd is valid
socket bind failed...
Error code: 22

如果我从此代码创建C程序，则作为常规C程序，gcc ...＆amp;＆amp; A.Out - ＆gt;然后不会发生错误。有什么原因？

可以是因为文件描述符已关闭吗？

Answer 1

问题在于，您将af_unix套接字视为af_inet一个。您不能使用sockaddr_in作为af_unix套接字，也无法将其绑定到IP地址。

我认为您已经在套接字定义代码中制作了错字。而不是

if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {

它应该是

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {