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Full Discussion: Need help about read() and write() on TCP/IP
Top Forums Programming Need help about read() and write() on TCP/IP Post 302469543 by lixiao1212 on Saturday 6th of November 2010 10:27:09 PM
Old 11-06-2010
Need help about read() and write() on TCP/IP
HI

I need to implement a client/server TCP application. the customer is the client and the bartender is the server.

When the customer enter the Bar, client connects to the server
Server should reply the client immediately. Other wise if the server is busy, it should send an update message every 10 seconds.

Depending on which message replied by the server:

10 seconds expired, no reply: client leave, that is disconnect
server is busy update: client reply --waiting or "leave and disconnect"
select beer: client reply -- light or black
select quantity: client reply liter or bottle, then disconnect

I have done the part before 'connection', but i don't know how to complement the function about read() and write(), so, please help me have a look at it, many thanks!!
Code:
#include <sys/wait.h>
#include <malloc.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <errno.h>
#include <stdlib.h>
#include <arpa/inet.h>
int main(int argc, char *argv[])
{
    int   socket1,n;   
        int blond=0 , brun=0;//string buf;
    char buffer[256];
    if(argc<2) {
        printf ("usage socket_clt \n");
        exit(0);
    }
 
    printf("client1 is coming\n");
        struct sockaddr_in local;
        struct sockaddr_in from;
        int fromlen =sizeof(from);
    bzero(&from, sizeof(from));
        from.sin_family=AF_INET;
        from.sin_port=htons(5000); //lisening 5000
        from.sin_addr.s_addr=INADDR_ANY; //address of local computer
    /*creat a socket*/   
    if (( socket1=socket(AF_INET, SOCK_STREAM,0))<0)
         {
        printf("socket error ourverture\n");exit(0);
    }
 
    if (connect(socket1, (struct sockaddr*)&from, sizeof(from))<0)
         {
        printf("socket error connection\n");
        exit(0);
    }
 
    bzero(buffer,256);
      fgets(buffer,255,stdin);
      n = write(socket1,buffer,strlen(buffer));
      if (n < 0)
           error("ERROR writing to socket");
 
  bzero(buffer,256);
      n = read(socket1,buffer,255);
      if (n < 0)
           error("ERROR reading from socket");
      printf("%s\n",buffer);
      return 0;
 
}

I need to add a function of 'timeout' on read(),but i don't know how to do that.
thus how can i add a circle to implement many customers entering?
Last edited by lixiao1212; 11-07-2010 at 03:20 PM.. Reason: Please use code tags
 

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LEARN ABOUT CENTOS

tcp_table

TCP_TABLE(5)							File Formats Manual						      TCP_TABLE(5)

NAME

       tcp_table - Postfix client/server table lookup protocol

SYNOPSIS

       postmap -q "string" tcp:host:port

       postmap -q - tcp:host:port <inputfile

DESCRIPTION

       The  Postfix mail system uses optional tables for address rewriting or mail routing. These tables are usually in dbm or db format. Alterna-
       tively, table lookups can be directed to a TCP server.

       To find out what types of lookup tables your Postfix system supports use the "postconf -m" command.

       To test lookup tables, use the "postmap -q" command as described in the SYNOPSIS above.

PROTOCOL DESCRIPTION

       The TCP map class implements a very simple protocol: the client sends a request, and the server sends one reply. Requests and  replies  are
       sent as one line of ASCII text, terminated by the ASCII newline character. Request and reply parameters (see below) are separated by white-
       space.

       Send and receive operations must complete in 100 seconds.

REQUEST FORMAT

       Each request specifies a command, a lookup key, and possibly a lookup result.

       get SPACE key NEWLINE
	      Look up data under the specified key.

       put SPACE key SPACE value NEWLINE
	      This request is currently not implemented.

REPLY FORMAT

       Each reply specifies a status code and text. Replies must be no longer than 4096 characters including the newline terminator.

       500 SPACE text NEWLINE
	      In case of a lookup request, the requested data does not exist.  In case of an update request, the request was rejected.	 The  text
	      describes the nature of the problem.

       400 SPACE text NEWLINE
	      This indicates an error condition. The text describes the nature of the problem. The client should retry the request later.

       200 SPACE text NEWLINE
	      The request was successful. In the case of a lookup request, the text contains an encoded version of the requested data.

ENCODING

       In request and reply parameters, the character %, each non-printing character, and each whitespace character must be replaced by %XX, where
       XX is the corresponding ASCII hexadecimal character value. The hexadecimal codes can be specified in any case (upper, lower, mixed).

       The Postfix client always encodes a request.  The server may omit the encoding as long as the reply is guaranteed to not contain the  %	or
       NEWLINE character.

SECURITY

       Do not use TCP lookup tables for security critical purposes.  The client-server connection is not protected and the server is not authenti-
       cated.

BUGS

       Only the lookup method is currently implemented.

       The client does not hang up when the connection is idle for a long time.

SEE ALSO

       postmap(1), Postfix lookup table manager
       regexp_table(5), format of regular expression tables
       pcre_table(5), format of PCRE tables
       cidr_table(5), format of CIDR tables

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview

LICENSE

       The Secure Mailer license must be distributed with this software.

AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

																      TCP_TABLE(5)
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