Socket connection between Java and C

Question

I want to establish socket connection between Java client and C server (on Unix). Can anybody tell how to do it? Will the socket created in client be available in server. I tried out but there was no response from the server.

Answer 1

We too can't connect the daemon server written by "c". The phenomena is below.
<< Execution of this Question1.class >> ---------------------------------------
[kazuyuki@CryptOne tmp]$ java Question1 E 1.2.3.4 MFrame.java 195.211.1.1 15021
<< Output message >> ----------------------------------------------------------
Quetion1 : flg_ = E
Quetion1 : key_ = 1.2.3.4
Quetion1 : fn_ = MFrame.java
Quetion1 : adr_ = CryptOne.localhost/195.211.1.1
Quetion1 : port_ = 15021
java.net.ConnectException: Connection refused
     at java.net.PlainSocketImpl.socketConnect(Native Method)
     at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:350)
     at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:137)
     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:124)
     at java.net.Socket.<init>(Socket.java:268)
     at java.net.Socket.<init>(Socket.java:122)
     at Question1.UPLOAD(Question1.java:65)
     at Question1.main(Question1.java:155)
<< Question >> ----------------------------------------------------------------
Why the event "java.net.ConnectException: Connection refused" has occured ?
The server to connect from Question1 can accept the connection request from
the client program coded by "c" program. We have written down the daemon server
program by "c" code tcp/ip socket functions (socket, bind, listen, accept).
Security manager admits the access from this Question1.class, we have checked.
Would you like please answer this Connction refuse occurrence ?
                                                                 2002.05.18 11:50:00.0(JST)
                                                                 K.Masuda
<< Java client code>> -------------------------------------------------
     (c)Copyright     All rights reserved.
          K.Masuda     2002.05.18
               << Question1.java >>
import     java.lang.String;
import     java.io.InputStream;
import     java.io.OutputStream;
import     java.io.DataInputStream;
import     java.io.DataOutputStream;
import     java.io.FileInputStream;
import     java.io.FileOutputStream;
import     java.io.IOException;
import     java.io.FileNotFoundException;
import     java.net.Socket;
import     java.net.InetAddress;
import     java.net.UnknownHostException;
import     java.net.ConnectException;
import     java.net.NoRouteToHostException;
class Question1 {
     char               flg_;
     String               key_;
     String               fn_;
     InetAddress          adr_;
     int                    port_;
     Socket               sock_;
     Question1(
          char          flg,
          String          key,
          String          fn,
          String          adr,
          int               port
          flg_     = flg;     
          key_     = key;
          fn_          = fn;
          try{
               adr_     = InetAddress.getByName( adr );
          catch( UnknownHostException e ){
               e.printStackTrace();
          port_     = port;
System.out.println( "Quetion1 : flg_ = " + flg_ );
System.out.println( "Quetion1 : key_ = " + key_ );
System.out.println( "Quetion1 : fn_ = " + fn_ );
System.out.println( "Quetion1 : adr_ = " + adr_ );
System.out.println( "Quetion1 : port_ = " + port_ );
     public void UPLOAD(
          try{
               sock_     = new Socket( adr_, port_ );
               UpLoad();
               DnLoad();
               sock_.close();
          catch( UnknownHostException e ){
               e.printStackTrace();
          catch( ConnectException e ){
               e.printStackTrace();
          catch( NoRouteToHostException e ){
               e.printStackTrace();
          catch( IOException e ){
               e.printStackTrace();
     public void UpLoad(
          byte[]                         buf          = new byte[ 512 ];
          int                              rlen;
          int                              wlen;
          try {
               OutputStream          sos          = sock_.getOutputStream();
               FileInputStream          fis          = new FileInputStream( fn_ );
               DataInputStream          dis          = new DataInputStream( fis );
               DataOutputStream     dos          = new DataOutputStream( sos );
               while( ( rlen =     dis.read( buf, 0, buf.length ) ) >= 0 ){
                    dos.write( buf, 0, rlen );
               dis.close();
               dos.close();
               fis.close();
               sos.close();
          catch( IOException e ){
               e.printStackTrace();
     public void DnLoad(
          byte[]                         buf          = new byte[ 512 ];
          int                              rlen;
          int                              wlen;
          try {
               InputStream               sis          = sock_.getInputStream();
               FileOutputStream     fos          = new FileOutputStream( fn_ + ".cry" );
               DataInputStream          dis          = new DataInputStream( sis );
               DataOutputStream     dos          = new DataOutputStream( fos );
               while( ( rlen =     dis.read( buf, 0, buf.length ) ) >= 0 ){
                    dos.write( buf, 0, rlen );
               dis.close();
               dos.close();
               fos.close();
               sis.close();
          catch( IOException e ){
               e.printStackTrace();
     public static void main(
          String[] args
          char[]     chrs     = ( new String( args[ 0 ] ) ).toCharArray();
          Question1     clnt     = new Question1(
                                                                 // E or D
                                        chrs[ 0 ],
                                        args[ 1 ],               // key string
                                        args[ 2 ],               // file to be processed
                                        args[ 3 ],               // IP address
                                                                 // port
                                        Integer.parseInt( args[ 4 ] )
          clnt.UPLOAD();
}