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POdebugging C native function android ndk - sendto()
 

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  1. POdebugging C native function android ndk - sendto()
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    <p>I've implemented a C native function with for android NDK, to send UDP packets. I have a working receiver but i seem to get nothing when i use the sender.</p> <ul> <li>How can i get more info from the return value of sendto? I'm having a hard time debugging native functions - no "debug step mode"</li> <li>can anyone see anything wrong about the sender code? is there something im not doing right?</li> </ul> <p>Thanks!</p> <pre><code>jstring Java_com_example_adhocktest_SenderUDP_SendUdpJNI( JNIEnv* env, jobject thiz, jstring ip, jstring message) { int PORT = 8888; int i; int sock_fd; char *_ip = (*env)-&gt;GetStringUTFChars(env, ip, 0); char *send_buf = (*env)-&gt;GetStringUTFChars(env, message, 0); //////////////// //////// create socket //////////////// if (( sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) &lt; 0 ) { return (*env)-&gt;NewStringUTF(env,"Cannot create socket"); } struct sockaddr_in myaddr; //////////////// //////// send //////////////// struct sockaddr_in servaddr; memset((char*)&amp;servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = 8888; if ((inet_aton(_ip,&amp;servaddr.sin_addr)) == 0) { return (*env)-&gt;NewStringUTF(env,"Cannot decode IP address"); } int retval = sendto(sock_fd, send_buf, strlen(send_buf), 0, (struct sockaddr*)&amp;servaddr, sizeof(servaddr)); close(sock_fd); char str[100]; if ( retval &lt; 0) { sprintf(str, "sendto failed with %d", retval); } else { sprintf(str, "sendto success with %d", retval); } return (*env)-&gt;NewStringUTF(env,str); } </code></pre>
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    1. COuse logging to logcat: http://stackoverflow.com/questions/4629308/any-simple-or-easy-way-to-debug-android-ndk-code
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    2. COI did use logcat but i got a correct return value from sendto(). ---Found the solution----- servaddr.sin_port = htons(8888); I dont fully understand the whole htons thing so if anyone could elaborate it would be lovely.
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