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digitalmars.D - strange problem with socket.accept()

reply Charma <Motoko_Kusanagi web.de> writes:
hello,
I have a very strange problem with the accept function of TpcSocket. I
programmed a mini-server who is waiting for a user and does something as soon a
user has connected(this has no concern) anyway, i got this part of code:

...
scope TcpSocket server = new TcpSocket( );
Socket user;
server.blocking(true);
server.bind( addr );
server.listen( 10 );

...
while(!killServer)
{
writef( "Waiting for user..." ); // **
user = server.accept( );
writef("[OK]")
...
}

Now my problem is that the line marked with ** is only displayed when a user
connects... which is very strange... i can't figure out the problem, since i
tell him to FIRST write that line and THEN wait for a user...

Any ideas?
thanks
May 30 2007
parent reply Paul Findlay <r.lph50+d gmail.com> writes:
 while(!killServer)
 {
 writef( "Waiting for user..." ); // **
 user = server.accept( );
 writef("[OK]")
 ...
 }

 Now my problem is that the line marked with ** is only displayed when a
 user connects... which is very strange... i can't figure out the problem,
 since i tell him to FIRST write that line and THEN wait for a user...
 Any ideas?

to connect until writef next called, whereupon the buffered output may be flushed? Maybe try something like the following instead import std.c.stdio; // ... while(/*...*/) { writef( "Waiting for user..." ); fflush(stdout); // or flushall(); // ... } Yes, I am just guessing. Perhaps best to ask in digitalmars.D.learn - Paul
May 30 2007
parent reply Charma <Motoko_Kusanagi web.de> writes:
Paul Findlay Wrote:

 while(!killServer)
 {
 writef( "Waiting for user..." ); // **
 user = server.accept( );
 writef("[OK]")
 ...
 }

 Now my problem is that the line marked with ** is only displayed when a
 user connects... which is very strange... i can't figure out the problem,
 since i tell him to FIRST write that line and THEN wait for a user...
 Any ideas?

to connect until writef next called, whereupon the buffered output may be flushed? Maybe try something like the following instead import std.c.stdio; // ... while(/*...*/) { writef( "Waiting for user..." ); fflush(stdout); // or flushall(); // ... } Yes, I am just guessing. Perhaps best to ask in digitalmars.D.learn - Paul

i do know that accept blocks... but it is called AFTER the writef... so it should black AFTER it... i still don't get it...
May 30 2007
parent reply Regan Heath <regan netmail.co.nz> writes:
Charma Wrote:
 Paul Findlay Wrote:
 
 while(!killServer)
 {
 writef( "Waiting for user..." ); // **
 user = server.accept( );
 writef("[OK]")
 ...
 }

 Now my problem is that the line marked with ** is only displayed when a
 user connects... which is very strange... i can't figure out the problem,
 since i tell him to FIRST write that line and THEN wait for a user...
 Any ideas?

to connect until writef next called, whereupon the buffered output may be flushed? Maybe try something like the following instead import std.c.stdio; // ... while(/*...*/) { writef( "Waiting for user..." ); fflush(stdout); // or flushall(); // ... } Yes, I am just guessing. Perhaps best to ask in digitalmars.D.learn - Paul

i do know that accept blocks... but it is called AFTER the writef... so it should black AFTER it... i still don't get it...

I am fairly sure it is output buffering (as Paul suggested). Change writef to writefln (I believe the output code flushes itself when a newline is sent). Failing that manually flushing as Paul mentioned should fix it. To explain, you call writef, it puts that in the output buffer but does not flush that to the screen. You call accept, this waits for a connection, a connection arrives and (for some reason) the output buffer gets flushed, perhaps because the socket code flushes all handles at some stage? Regan
May 30 2007
parent Charma <Motoko_Kusanagi web.de> writes:
Regan Heath Wrote:

 Charma Wrote:
 Paul Findlay Wrote:
 
 while(!killServer)
 {
 writef( "Waiting for user..." ); // **
 user = server.accept( );
 writef("[OK]")
 ...
 }

 Now my problem is that the line marked with ** is only displayed when a
 user connects... which is very strange... i can't figure out the problem,
 since i tell him to FIRST write that line and THEN wait for a user...
 Any ideas?

to connect until writef next called, whereupon the buffered output may be flushed? Maybe try something like the following instead import std.c.stdio; // ... while(/*...*/) { writef( "Waiting for user..." ); fflush(stdout); // or flushall(); // ... } Yes, I am just guessing. Perhaps best to ask in digitalmars.D.learn - Paul

i do know that accept blocks... but it is called AFTER the writef... so it should black AFTER it... i still don't get it...

I am fairly sure it is output buffering (as Paul suggested). Change writef to writefln (I believe the output code flushes itself when a newline is sent). Failing that manually flushing as Paul mentioned should fix it. To explain, you call writef, it puts that in the output buffer but does not flush that to the screen. You call accept, this waits for a connection, a connection arrives and (for some reason) the output buffer gets flushed, perhaps because the socket code flushes all handles at some stage? Regan

ok, i got it now! fflush fixed it, thanks a lot!
May 30 2007