connect error of socket programming via ndk

Question

Actually,i have do a test with the server.c and client.c in the android emulator(ps:they both runs sucesssfully and are compiled with the android genric cross-compiler).And,then i go further,i rewrite the client-side via the jni.But,in this case,the client fail to connect to the server-side,though new client is very similar to the client.c. After searching,someone mentions that the permission matters.But,when i add the <uses-permission android:name="android.permission.INTERNET" />(ps：this tags is outside the application tags),the problem still appears. And as the logcat shows,the java code actually invode the c method,but,why not it behave the same as the client.c? Any idea will benefit me so much。Thanks in advance!

the server.c:

/*  Make the necessary includes and set up the variables.  */

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>

int main()
{
    int server_sockfd, client_sockfd;
    int server_len, client_len;
    struct sockaddr_un server_address;
    struct sockaddr_un client_address;

/*  Remove any old socket and create an unnamed socket for the server.  */

    unlink("server_socket");
    server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0);

/*  Name the socket.  */

    server_address.sun_family = AF_UNIX;
    strcpy(server_address.sun_path, "server_socket");
    server_len = sizeof(server_address);
    bind(server_sockfd, (struct sockaddr *)&server_address, server_len);

/*  Create a connection queue and wait for clients.  */

    listen(server_sockfd, 5);
    while(1) {
        char ch;

        printf("server waiting\n");

/*  Accept a connection.  */

        client_len = sizeof(client_address);
        client_sockfd = accept(server_sockfd, 
            (struct sockaddr *)&client_address, &client_len);

/*  We can now read/write to client on client_sockfd.  */

        read(client_sockfd, &ch, 1);
        ch++;
        write(client_sockfd, &ch, 1);
        close(client_sockfd);
    }
}

client.c:

/*  Make the necessary includes and set up the variables.  */

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>

int main()
{
    int sockfd;
    int len;
    struct sockaddr_un address;
    int result;
    char ch = 'A';

/*  Create a socket for the client.  */

    sockfd = socket(AF_UNIX, SOCK_STREAM, 0);

/*  Name the socket, as agreed with the server.  */

    address.sun_family = AF_UNIX;
    strcpy(address.sun_path, "server_socket");
    len = sizeof(address);

/*  Now connect our socket to the server's socket.  */

    result = connect(sockfd, (struct sockaddr *)&address, len);

    if(result == -1) {
        perror("oops: client1");
        exit(1);
    }

/*  We can now read/write via sockfd.  */

    write(sockfd, &ch, 1);
    read(sockfd, &ch, 1);
    printf("char from server = %c\n", ch);
    close(sockfd);
    exit(0);
}

java code: package gz.kaiwii;

public class NSocket {
    static{
        System.loadLibrary("NSocket");
    }
    public native void start();
}

native code:

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
#include <android/log.h>
#include <android/bitmap.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>

#define  LOG_TAG    "NSocket"
#define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)



JNIEXPORT void JNICALL Java_gz_kaiwii_NSocket_start
  (JNIEnv * env, jobject object){
    LOGI("JNICALL Java_gz_kaiwii_NSocket_start is called!");

    int sockfd;
    int len;
    struct sockaddr_un address;
    int result;
    char ch = 'A';

/*  Create a socket for the client.  */

    LOGI(" Create a socket for the client!");

    sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
    if(sockfd==-1){
    LOGE("create socket error!!!!!");
}

/*  Name the socket, as agreed with the server.  */

    address.sun_family = AF_UNIX;
    strcpy(address.sun_path, "server_socket");
    len = sizeof(address);

/*  Now connect our socket to the server's socket.  */

    result = connect(sockfd, (struct sockaddr *)&address, len);

    LOGI("  Now connect our socket to the server's socket.");

    if(result == -1) {
        LOGE("connect error!");
        exit(1);
    }


/*  We can now read/write via sockfd.  */

    write(sockfd, &ch, 1);
    read(sockfd, &ch, 1);
    /*
    printf("char from server = %c\n", ch);
    */
    LOGI("char from server = %c\n", ch);
    close(sockfd);
}

the logcat:

Answer 1

If I use the abstract namespace as the name,everything runs okay.But,one thing should be cautioned is the length!