通过JNI绑定Socket

Question

我尝试通过JNI在Linux机器上打开一个套接字连接。如果我将Java_Socket_socket和Java_Socket_bind组合在同一个C函数中，JNI调用可以完美地工作，但是当我按顺序运行方法时，它就不起作用了。

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: %dn", 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 - %dn", 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 - %dn", 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 - %dn", sizeof(servaddr));
if (fcntl(c_sockfd, F_GETFD) != -1 || errno != EBADF) {
printf("fd is validn");
} else {
printf("fd is invalidn");
}
// 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: %dn", 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

如果我从这段代码创建C程序，并且作为普通的C程序，gcc ... && a.out->然后没有错误发生。什么是理性?

可能是因为文件描述符已关闭吗?

Answer 1

问题是您将AF_UNIX套接字视为AF_INET套接字。AF_UNIX套接字不能使用sockaddr_in，也不能绑定到IP地址。

我认为你在套接字定义代码中打了一个错别字。而不是

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

应该是

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