Hi, everyone!
I thought I posted the code first, it's better. This is the code of the program I've worked with :

#include "liveMedia.hh"
#include "BasicUsageEnvironment.hh"
#include <stdio.h>

UsageEnvironment* env;
Boolean reuseFirstSource = False;
Boolean iFramesOnly = False;

static void announceStream(RTSPServer* rtspServer, ServerMediaSession* sms,
			   char const* streamName, char* inputFileName); // fwd

char* getFileName(int choice);
char* getFileName(int choice)
{
	char* inputFile = "";
	switch(choice){
		case 1: inputFile = "A.mp3";
			break;
		case 2: inputFile = "B.mp3";
			break;
		case 3: inputFile = "C.mp3";
			break;
	}
return inputFile;
}
int main(int argc, char** argv) {
  // Begin by setting up our usage environment:
  TaskScheduler* scheduler = BasicTaskScheduler::createNew();
  env = BasicUsageEnvironment::createNew(*scheduler);

  UserAuthenticationDatabase* authDB = NULL;
#ifdef ACCESS_CONTROL
  // To implement client access control to the RTSP server, do the following:
  authDB = new UserAuthenticationDatabase;
  authDB->addUserRecord("username1", "password1"); // replace these with real strings
  // Repeat the above with each <username>, <password> that you wish to allow
  // access to the server.
#endif

  // Create the RTSP server:
  RTSPServer* rtspServer = RTSPServer::createNew(*env, 8554, authDB, 45);
  if (rtspServer == NULL) {
    *env << "Failed to create RTSP server: " << env->getResultMsg() << "\n";
    exit(1);
  }

  char const* descriptionString = "Session streamed by \"testOnDemandRTSPServer\"";
{
    char const* streamName = "mp3AudioTest";
    char* inputFileName=argv[100];
    ServerMediaSession* sms
      = ServerMediaSession::createNew(*env, streamName, streamName, descriptionString);
    Boolean useADUs = False;
    Interleaving* interleaving = NULL;
#ifdef STREAM_USING_ADUS 
    useADUs = True;
#ifdef INTERLEAVE_ADUS
    unsigned char interleaveCycle[] = {0,2,1,3}; // or choose your own...
    unsigned const interleaveCycleSize
      = (sizeof interleaveCycle)/(sizeof (unsigned char));
    interleaving = new Interleaving(interleaveCycleSize, interleaveCycle); 
#endif
#endif
    sms->addSubsession(MP3AudioFileServerMediaSubsession::createNew(*env, inputFileName, reuseFirstSource, useADUs, interleaving));
    rtspServer->addServerMediaSession(sms);
    announceStream(rtspServer, sms, streamName, inputFileName);
  }
env->taskScheduler().doEventLoop(); // does not return

  return 0; // only to prevent compiler warning
}

static void announceStream(RTSPServer* rtspServer, ServerMediaSession* sms,
			   char const* streamName, char* inputFileName) {
  char* url = rtspServer->rtspURL(sms);
  UsageEnvironment& env = rtspServer->envir(); 
 int choice;
	env << "Which file to play?\r\n";
	env << "Menu : \n";
	env << "1. A\n";
	env << "2. B\n";
	env << "3. C\n";
	scanf("%d", &choice);

  inputFileName = getFileName(choice);
  env << "\n\"" << streamName << "\" stream, from the file \""
      << inputFileName << "\"\n";
  env << "Play this stream using the URL \"" << url << "\"\n";
	
	
  delete[] url;
}

After that I compiled it, and the output is like this :

Which file to play?
Menu : 
1. A
2. B
3. C
3

"mp3AudioTest" stream, from the file "C.mp3"
Play this stream using the URL "rtsp://10.10.10.101:8554/mp3AudioTest"
Segmentation fault (core dumped)

Ok. Now I talk about the functionality of the program :
This is the program that let the user choose the audio file, then play. I pull up the server first, choose the file name (as you see, I enter "3" and the file name returned is "C.mp3"). After that, I open the client and play the file. But it can't play and server returned message : Segmentation fault (core dumped)

I do a Google search and I found that this caused by pointer error (using non-pointer for pointer, maybe not exactly what I read, because I can't find the article which talk about this again). I re-check my program, but can't see where is the pointer error.

May everyone give me a hand on this problem? Thanks a lot.

>> char* inputFileName=argv[100];
Huh? Do you pass over 100 arguments on the command line to your program? Not very likely, so that are you trying to do here ?

Hmm...only 1 argument. I thought I typed wrong here. So how can I correct the message "Segmentation fault (core dumped)"?

> I thought I typed wrong here.
What!!???

You mean that code isn't a direct copy/paste from your code editor?

Because if it isn't, you're wasting everyone's time.

> char* url = rtspServer->rtspURL(sms);
Post that method.
Are you sure that delete [] url; is valid at that point?

> char* inputFileName=argv[100];
Notwithstanding the point AD made, you also seem to use this as some local variable for reading in user input as well.
Try using a true std::string for reading input.
Ditto with your use of scanf, use a C++ equivalent.

The code is the same to my code editor. This is the code that I modified from another code. The original one works well, but can play only the file which has the name defined in the code. If I want to play another file, I want to go back to the code, change the name, compile again then play. It's not convenient, so I want to modify the source code to be able to play different files. The lines I added are ;

char* getFileName(int choice);
char* getFileName(int choice)
{
	char* inputFile = "";
	switch(choice){
		case 1: inputFile = "A.mp3";
			break;
		case 2: inputFile = "B.mp3";
			break;
		case 3: inputFile = "C.mp3";
			break;
	}
return inputFile;
}

And :

char* inputFileName=argv[100]; (this is actually argv[1], not [100])

And

int choice;
	env << "Which file to play?\r\n";
	env << "Menu : \n";
	env << "1. A\n";
	env << "2. B\n";
	env << "3. C\n";
	scanf("%d", &choice);

  inputFileName = getFileName(choice);

If I take out all these, the code will work again, but can't choose different files.

@Salem : yes, I use the "char* inputFileName=argv[1] " as the variable to read the user input.
Is it the error caused by this variable?

Well if your user input is going into where argv[1] is stored, and you type in a longer name, or you don't supply an argument and you type something (anything) in, then yes, your code is in trouble.

I has just changed positions of codes and add some lines, it works now. Thank Salem for your advice.

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