TCP connection with Sockets....

I have read the documentation for Sockets and stuff, yet I still dont quite understand how to use them..
I am creating an instant message program. It is my understanding that I need a ServerSocket that listens to the port and a regular Socket which sends data to the other user.. Correct?
Diagram:
        Computer1                                                         Computer2
   ServerSocket <------ P                                P
                                       O <<---------------->>O <----------Socket
   Socket --------------> R                                R
                                       T                                T -------> ServerSocketI dont know if that will turn out right or not, there are alot of spaces..

PrintWriter would work as long as you're only using characters. An image, for example, would not work with PrintWriter but character based communication would.
As far as connecting back and forth: it is easy enough for one of the process to act as just a server and one or more clients connect. It is all about who can initiate a conversation.
Say you use a traditional client/server setup. The server sits and waits for a connection. Say this is user1. Then, user2 fires up his program and connects to the server. Now user1 and user2 can have a conversation on a single Socket since this is two way.
But the problem with this is that user1 can't talk to user2 unless user2 initiates a conversation. If you want it where user1 can initiate the conversation and user2 can do the same then you will need a ServerSocket in each process.
If this is a school project then this is fine but the major headache you'd run into of this scaled to, say, 10 users is that you'd have a heck of a time managing where all the processes are and on what port. Picture a drawing with 10 points in a circle and a line drawn from each point to all others and you'll get the idea quickly.

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Creating a TCP connection with SSL/TLS

Hi,
I am working in a application that depends on the server. I need to estabilish a TCP connection with SSL/Tls secure connection with the server in order to get the datas.
I have the following code structure :
- (id)initWithHostAddressNSString*)_host andPortint)_port
[self clean];
self.host = _host;
self.port = _port;
CFWriteStreamRef writeStream;
CFReadStreamRef readStream;
return self;
-(BOOL)connect
if ( self.host != nil )
// Bind read/write streams to a new socket
CFStreamCreatePairWithSocketToHost(kCFAllocatorDef ault, (CFStringRef)self.host, self.port, &readStream, &writeStream);
return [self setupSocketStreams];
- (BOOL)setupSocketStreams
// Make sure streams were created correctly
if ( readStream == nil || writeStream == nil )
[self close];
return NO;
// Create buffers ---- has not been released , so need to check possible ways to release in future
incomingDataBuffer = [[NSMutableData alloc] init];
outgoingDataBuffer = [[NSMutableData alloc] init];
// Indicate that we want socket to be closed whenever streams are closed
CFReadStreamSetProperty(readStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);
CFWriteStreamSetProperty(writeStream, kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);
//Indicate that the connection needs to be done in secure manner
CFReadStreamSetProperty(readStream, kCFStreamPropertySocketSecurityLevel, kCFStreamSocketSecurityLevelNegotiatedSSL);
CFWriteStreamSetProperty(writeStream, kCFStreamPropertySocketSecurityLevel, kCFStreamSocketSecurityLevelNegotiatedSSL);
// We will be handling the following stream events
CFOptionFlags registeredEvents = kCFStreamEventOpenCompleted |
kCFStreamEventHasBytesAvailable | kCFStreamEventCanAcceptBytes |
kCFStreamEventEndEncountered | kCFStreamEventErrorOccurred;
// Setup stream context - reference to 'self' will be passed to stream event handling callbacks
CFStreamClientContext ctx = {0, self, NULL, NULL, NULL};
// Specify callbacks that will be handling stream events
BOOL doSupportAsync = CFReadStreamSetClient(readStream, registeredEvents, readStreamEventHandler, &ctx);
BOOL doSupportAsync1 = CFWriteStreamSetClient(writeStream, registeredEvents, writeStreamEventHandler, &ctx);
NSLog(@"does supported in Asynchrnous format? : %d :%d", doSupportAsync, doSupportAsync1);
// Schedule streams with current run loop
CFReadStreamScheduleWithRunLoop(readStream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
CFWriteStreamScheduleWithRunLoop(writeStream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
// Open both streams
if ( ! CFReadStreamOpen(readStream) || ! CFWriteStreamOpen(writeStream))
// close the connection
return NO;
return YES;
// call back method for reading
void readStreamEventHandler(CFReadStreamRef stream,CFStreamEventType eventType, void *info)
Connection* connection = (Connection*)info;
[connection readStreamHandleEvent:eventType];
// call back method for writing
void writeStreamEventHandler(CFWriteStreamRef stream, CFStreamEventType eventType, void *info)
Connection* connection = (Connection*)info;
[connection writeStreamHandleEvent:eventType];
`
As above, I have used
CFReadStreamSetProperty(readStream, kCFStreamPropertySocketSecurityLevel, kCFStreamSocketSecurityLevelSSLv3);
CFWriteStreamSetProperty(writeStream, kCFStreamPropertySocketSecurityLevel, kCFStreamSocketSecurityLevelSSLv3);
in order to make a secured connection using sockets.
The url i am using is in the format "ssl://some domain.com"
But in my call back method i am always getting only kCFStreamEventErrorOccurred for CFStreamEventType .
I also tried with the url "https://some domain.com" ,but getting the same error.
i also commented out setting kCFStreamPropertySocketSecurityLevel, but still i am receiving the same error that i mentioned above.
I dont know how it returns the same error. I have followed the api's and docs , but they mentioned the same way of creating a connection as i had given above.
I tried to get the error using the following code :
CFStreamError error = CFWriteStreamGetError(writeStream);
CFStreamErrorDomain errDomain = error.domain;
SInt32 errCode = error.error;
The value for errCode is 61 and errDomain is kCFStreamErrorDomainPOSIX. so i checked out the "errno.h", it specifies errCode as "Connection refused"
I need a help to fix this issue.
If the above code is not the right one,
**(i)how to create a TCP connection with SSL/TLS with the server.**
**(ii)How the url format should be(i.e its "ssl://" or "https://").**
**(iii)If my above code is correct where lies the error.**
I hope the server is working properly. Because I can able to communicate with the server and get the datas properly using BlackBerry and android phones. They have used SecuredConnection api's built in java. Their url format is "ssl://" and also using the same port number that i have used in my code.
Any help would be greatly appreciated.
Regards,
Mohammed Sadiq.

Hello Naxito. Welcome to the Apple Discussions!
Try the following ...
Perform a "factory default" reset of the AX
o (ref: http://docs.info.apple.com/article.html?artnum=108044)
Setup the AX
Connect to the AX's wireless network, and then, using the AirPort Admin Utility, try these settings:
AirPort tab
o Base Station Name: <whatever you wish or use the default>
o AirPort Network Name: <whatever you wish or use the default>
o Create a closed network (unchecked)
o Wireless Security: Not enabled
o Channel: Automatic
o Mode: 802.11b/g Compatible
Internet tab
o Connect Using: Ethernet
o Configure: Manually
o IP address: <Enter your college-provided IP address>
o Subnet mask: <Enter your college-provided subnet mask IP address>
o Router address: <Enter your college-provided router IP address>
o DNS servers: <Enter your college-provided DNS server(s)
o WAN Ethernet Port: Automatic
<b>Network tab
o Distribute IP addresses (checked)
o Share a single IP address (using DHCP & NAT) (enabled)

How to control tcp connection with java tcp socket programing ??

Hi,
I am connecting a server as using java socket programming.
When server close the connection (socket object) as using close() method ,
I can not detect this and My program continue sending data as if there is a connection with server.
How to catch the closing connection ( socket ) with java socket programming.
My Client program is as following :
import java.io.PrintWriter;
import java.net.Socket;
public class client
public client()
   * @param args
public static void main(String[] args)
    Socket socket=null;
    PrintWriter pw=null;
    try
                      socket = new Socket("localhost",5555);
                      pw = new PrintWriter(socket.getOutputStream(),true);
                      int i=0;
                      while (true)
                        i++;
                        pw.println(i+". message is being send.");
                        Thread.sleep(5000);
    } catch (Exception ex)
                      ex.printStackTrace();
    } finally
                      try
                        if(pw!=null)pw.close();
                        if(socket!=null)socket.close();
                      } catch (Exception ex)
                        ex.printStackTrace();
                      } finally
}

I changed the code as following. But I couldn't catch the EOFException when I read from the socket. How can I catch this exception ?
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class client
public client()
   * @param args
public static void main(String[] args)
    Socket socket=null;
    PrintWriter pw=null;
    BufferedReader bufIn=null;
    InputStreamReader inRead=null;
    InputStream in=null;
    try
                      socket = new Socket("localhost",5555);
                      in = socket.getInputStream();
                      inRead = new InputStreamReader(in);
                      bufIn = new BufferedReader(inRead);
                      pw = new PrintWriter(socket.getOutputStream(),true);
                      int i=0;
                      while (true)
                        i++;
                        try
                          bufIn.readLine();
                          pw.println(i+". message is being send.");
                          System.out.println(i+". message has been send");
                        } catch (Exception ex2)
                          System.out.println(ex2.toString());
                          System.out.println(i+". message could not be send");
                        } finally
                        Thread.sleep(5000);
    } catch (EOFException ex)
                      ex.printStackTrace();
    } catch (InterruptedException ex)
                      ex.printStackTrace();
    } catch (IOException ex)
                      ex.printStackTrace();
    } finally
                      try
                        if(pw!=null)pw.close();
                        if(socket!=null)socket.close();
                      } catch (Exception ex)
                        ex.printStackTrace();
                      } finally
}

Connect to a printer via TCP connection with wifi

Hi,
what i would like to do, is to connect a printer to the iPhone via wireless.
The printer is in the same wifi as the iPhone and the ip adress is known.
So what i started to to is, to create a SocketConnection with CFStreamCreatePairWithSocketToHost(...). But if i switch of the printer, the inputstream is created too, and is not NULL as expected.
Is this the right approach im using or is there a better possibilty to send strings to my printer using a tcp connection over wifi?
Regards,
Grinarn

Welcome to Apple Discussions!
In the Help menu of the Finder is a little app called Mac Help. Most Apple apps and many 3rd party apps also use Mac Help. In Mac Help is an article called *Adding a printer shared by a Windows computer via SMB/CIFS*. This article is regarding sharing a printer that is connected to a PC over a network however, and not to a router, but may have info useful to troubleshooting. You might also check with your Linksys user guide for info on sharing this printer with a Mac over the network.

HTTP Connection with Sockets

Why does the response come back as nothing assume req="GET HTTP/1.0" and url="http://www.google.com".
String resp = "";
Socket s = null;
            Scanner in = null;
            BufferedWriter out = null;
            try
                URL u = new URL(url);
                int port = u.getPort();
                if(port < 1)
                    port = 80;
                s = new Socket(u.getHost(), port);
                out = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
                out.write(req, 0, req.length() - 1);
                out.flush();
                in = new Scanner(new InputStreamReader(s.getInputStream()));
                while(in.hasNext())
                    resp += in.nextLine() + "\n";
                System.out.println("RESP:" + resp);
            catch(Exception ex)
                resp = ex.toString();
                ex.printStackTrace();
                /*if(in != null)
                    in.close();
                if(out != null)
                    out.close();
                if(s != null)
                    s.close();
            }

chasepreuninger wrote:
But if my request is invalid shouldn't the google server send back an error code?It will only respond once it recognises a complete request. Your request is incomplete. Once you terminate it properly, you will get a response from the server (either the page you wanted, or an error, or something).

TCP connect consumes 80% of CPU load

Hello!
I've done some profiling on a Java application and i see that 80% of the time the application has on the CPU is used for establishing a TCP connection.
Socket c;
c.connect("",xxxx);The application performes several hundreds of connect per minute, but most of them take about 5 sec or less, but som uses the CPU for more than 130 seconds!!
Could, i suspect it too be a problem with the network card beeing overloaded and will try wit multiple NIC's. But does anybody have any experience with this??? and maybe point out some improvements.

Hello!
Should have mentioned it.. we are using a
ThreadPoolExecutor with 1000 threads in the core. But
shall look into that. thanx :-)
There may be some improvements that can be done in
that areaThis doesn't have anything to do with what I am talking about. I am talking about a pool of open connections (sockets) not a pool of working threads.
Here is the thing when you (in a program) tell a socket to close the OS gets told that the socket is no longer in use and should be closed. The OS then closes the socket but doesn't actually release the allocated resources until it feels like it. It feels like it when it (a) has some spare time with nothing else to do or (b) it has to reclaim the resources because something else needs them.
In short the OS final clean up of socket resources is rather akin to garbage collection by the JVM... it will happen but not neccessarily right away and you really can't do anything about that.
Let me make this 100% clear. This is NOT a Java problem. This is an OS "problem". Although it's not really a problem either. Under most sensible scenarios that model works just fine... your problem is that you are doing something foolish.
Creating and disposing of sockets is an intensive task for the OS. The queue of sockets waiting to be finally disposed of by the OS grows and grows while it is busy creating new sockets for you until eventually it HAS to clean up in order to give you a new socket. Then you pay a big penalty in time while the OS does it's garbage collection.
So in summary as it goes this situation is insolvable. What you need to do is not be creating and destroying hundreds of sockets every second. How can you do this? By using a pool of already open sockets that are shared among your various threads.

TCP connections on Cisco ASA disconnects the database session every 30 Minutes

Right after a firmware upgrade form 8.4.2 to 8.4.7 on our ASA 5540:
the database app that makes a tcp connection with the database loses connection to the database servers on the inside of the firewall
-Nothing changed on the process servers.
-Nothing but firmware version changed on the firewalls.
-Rebooting did not help.
-Connections don't always drop every 30 minutes, but it's still almost exactly at that time, with a 90% chance of it happening. And it reestablishes in about 52 second
-The client is not willingly terminating the connections to the database servers on the inside. The connection is just going away.

I am not seeing any error in the logs in ASA but in our client we see:
Latest from PROD (times are in UTC):
Sun Apr 13 10:22:10 2014 - ERR: Read from the server failed (err[36],sev[78],state[0],line[0],server[],proc[],sql[exec sp_events_insupd :p1,:p2,:p3,:p4,:p5,:p6,:p7,:p8,:p9,:p10,:p11,:p12,:p13,:p14,:p15,:p16,:p17],err_type[client])
Sun Apr 13 11:47:09 2014 - ERR: Read from the server failed (err[36],sev[78],state[0],line[0],server[],proc[],sql[exec sp_events_insupd :p1,:p2,:p3,:p4,:p5,:p6,:p7,:p8,:p9,:p10,:p11,:p12,:p13,:p14,:p15,:p16,:p17],err_type[client])

Can we use applets as user interfaces with sockets, RMI and J2EE

Dear Sir or Madam,
Since I am a TA for software architecture class, some one ask me the following question: I think the answer is "No" based on the document on http://java.sun.com/sfaq/
How I answer the quesions? Looking forward your help!!!
1.You may have 2 applets and 2 html files. One applet with one html file may stay at a client PC and run on this PC, and the other applet with the other html file may stay at a server PC and run on this PC. In this case, all the applets are run locally.
2.Could applets works with sockets, RMI and J2EE?
3.Can we use applets as user interfaces with sockets, RMI and J2EE?
Thank you very much!
Best regards,
Jing

The scenario you paint doesn't quite make sense. The "server PC" wouldn't be running an applet, normally, since applets are by definition in a web browser page, and most likely involve user interaction, and "server processes" generally are done without user interaction.
The security rules around applets are that -- by default -- applets can connect with sockets ONLY to the server from whence the applet was loaded. RMI uses sockets (J2EE is too broad a spec) and hence RMI calls would also be limited to the server from whence the applet was loaded. Within that limitation, an applet could open all the sockets it wants, so long as they are all on the server from whence the applet was loaded.
If you want two applets on two different systems to communicate with each other, the simplest way is to have them rendevous through a server process on the server(s) from whence each applet was loaded. Maybe it's PC-a <-> server-a <-> server-b <-> PC-b ...? Or maybe PC-a and PC-b both are talking to the same server.
The limitation is rooted in the security subsystem. You can specify a policy file and override anything in the security subsystem. That does mean signing the applet and then cajoling the user into agreeing to grant greater levels of security than the default. In such a case you can open sockets more broadly and then PC-a could talk directly to PC-b without going through any servers.
- David

Java Application Server 9 - TCP connections

I have installed Sun Java Application Server 9 and I see that the java process that is started has a lot (more than 30) of TCP connections with a local and a remote address that are both the hostname of the machine that run JAS.
Can someone tell me what are these connections and if there is a way to decrease the amount of these connections?
Thank you

I have installed Sun Java Application Server 9 and I see that the java process that is started has a lot (more than 30) of TCP connections with a local and a remote address that are both the hostname of the machine that run JAS.
Can someone tell me what are these connections and if there is a way to decrease the amount of these connections?
Thank you

FMS closing the TCP connection forcibly

Hi,
I am developing an live encoder programs to publish the audio and video content to FMS. After establishing the TCP connection with FMS, when i start sending commanda and data, FMS is closing the TCP connection forcibly. Can anyone explain why is this happening?
Thanks and Regards,
Vishwanath

Hi,
If you use wireshark you can see what is happening on the wire to capture what FMS is sending (if at all) back to your live encoder program. Very very useful tool.
BTW what version of FMS are you using? Have you tried FMLE 3.2 to ensure your setup is good to go as a benchmark, this ensures you have a working FMS server ready for your own live encoder program.
I hope this helps with your debugging.

TCP Connections vs TCP Flows

Hello:
I'm trying to track activity on a CSS11800 and have been watching TCP Connections with "sh serv summary" and TCP Flows with "sh flows 0.0.0.0". However, there doesn't appear to be any obvious correlation btw these figures.
Can anyone tell me which command will provide the most accurate picture of current user connections?
Does "sh serv summary" display both inbound and outbound connections whereas "sh flows 0.0.0.0 xx.xx.xx.xx" displays inbound connections only??
We often see high numbers of TCP Connections during off hours when there is no activity occuring. Perhaps this is case of browsers being left open which maintains the TCP flow.
Thanks for the insight.
Best regards,
Dan

Hi Gilles:
We have 3 service balanced to a single VIP for one client. We have been using the TCp Conn's from "show service summary" to gauge the activity of the client.
However, this number seems to fluctuate, but never actually goes below roughly 40 per service, even when there are no active flows to the VIP. And it never correlates directly to the number of flows. Would it count 2 conn's for each flow (inbound and outbound)?
Our HTTP keepalives are running as persistant - could this affect the TCP Conn's number?? Or perhaps it's an IOS issue?
Our test environments on both old IOS and 6.10 seem to display the TCP Conn's correctly, as in the number goes up and down with the creation and teardown of TCP flows. But, it seems on a loaded production environment.
Are there any particular concerns relating to the 5.02 image?? We are planning an upgrade very soon.
Regards,
Dan

WebStart & TCP connection.

My application needs to establish a TCP connection with a server. Although it now establishes connection only with the server it started from, for some reason I've digitally signed jar and requested full permissions in jnlp.
Now I see a very strange thing - although I can start jar from any machine and it works perfectly, when I try to start the same jar through WebStart it tears connection down. Server reports read timeout and application reports connection reset.
Again - the same jar works perfectly when started from local hard drive. jre version is 1.4.1_02, webstart version is 1.2. Tried to run from Windows2000 WS and Solaris 8 x86.

Oops. Sorry guys, the shame on my bald skull. I've set SOTimeout to 600ms, and it looks like WS created a slightly larger delay on permission checkup.
Now it works fine, thanks.

HP/Agilent Infiniium 54831B scope - how to connect with LabView 6.0 by LAN (TCP/IP)

Dear,
I'm looking inf. how to connect Agilent Infiniium 54831B scope with LabView 6.0 by LAN (TCP/IP).
Thanks in advance.
Regards,
Z.Mrowka
mailto:[email protected]

Hello,
If the instrument is capable of being controlled from its TCP/IP port, it will be possible to communicate with the instrument from LabVIEW using VISA.
The VISA resource name input will need to be entered manually and is a little different from the normal Serial or GPIB format. The format is as follows:
For SOCKET connections, this is just like the traditional TCP functionality in LabVIEW. An example string that connects with the NI FTP site is:
"TCPIP::ftp.ni.com::21:OCKET"
For INSTR connection, this requires a device that supports the T&M standard LAN instrument protocol. An example of this (that we have tested with) is the Tektronix 3054 Scope. A string that connects with this scope is: "TCPIP::HostnameOrIP::gpib0,1::INSTR"
I hope this
helps,
Anthony Bacak
National Instruments
Applications Engineering

TCP connection closed but a child process of SQL Server may be holding a duplicate of the connection's socket in SQL2008R2

Hello,
I do get the below SQL error in production environment intermittently:
TCP connection closed but a child process of SQL Server may be holding a duplicate of the connection's socket. Consider enabling the TcpAbortiveClose SQL Server registry setting and restarting SQL Server. If the problem persists, contact Technical
Support.
According to the post I search in MSDN, the above error is fixed in SQL2008R-CU6, but I have SQL2008R2-SP02 CU09 patch in production environment and the above error still occurred intermittently. I am running SQL2008R2 SP02 CU09 patch with Windows 2008R2-SP01.
I would like to know if anyone has the same error happened to their SQL environment after applied SQL2008R2-SP02 CU06 patch and later.
Any suggestion would be helpful.
Best regards,
PL.

Hello,
What happen if you apply the changes on the registry explained on the workaround section of the following article?
http://support.microsoft.com/kb/2491214
Hope this helps.
Regards,
Alberto Morillo
SQLCoffee.com

Crash connection over Internet using TCP/IP SSL sockets

I'm doing a file Transfer WEB Client/server Application using TCP/IP SSL Sockets?
In an internal LAN the file Transfer work pretty well but in Internet this Crash (downturn the file transfer).
the code in Client to connect to server is:
SSLSocketFactory sslFact = (SSLSocketFactory)SSLSocketFactory.getDefault();
socket = (SSLSocket)sslFact.createSocket(c.site, c.PORT);
String [] enabledCipher = socket.getSupportedCipherSuites ();
socket.setEnabledCipherSuites (enabledCipher);
out = new ObjectOutputStream(socket.getOutputStream());
in = new ObjectInputStream(socket.getInputStream());
The code in Server to wait client connections is:
Runtime.getRuntime().addShutdownHook(new ShutdownThread(this));
try {
SSLServerSocketFactory factory = (ServerSocketFactory) SSLServerSocketFactory.getDefault();
SSLServerSocket sslIncoming =
(SSLServerSocket) factory.createServerSocket (PORT);
String [] enabledCipher = sslIncoming.getSupportedCipherSuites ();
sslIncoming.setEnabledCipherSuites (enabledCipher);
while(running) {
SSLSocket s = (SSLSocket)sslIncoming.accept();
newUser(s, pauseSyn);
} catch (IOException e) { System.out.println("Error: " + e); }
Some help with this topic, show me the ligth? what is bad?

Hi,
Can you show us the stacktrace?
/Kaj

TCP connection with Sockets....

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