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IPC Using SOCKETS AF_INET

RCS file: server.c,v
Working file: server.c
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description:
Server implementaton using TCP , AF_INET.
>> Calls used : socket(), bind(), listen(), accept().
>> sockaddr_in
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revision 1.1
date: 2014/08/28 05:26:46;  author: root;  state: Exp;
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RCS file: client.c,v
Working file: client.c
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description:
AF_INET client program.
calls used: bind(), connect.
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revision 1.1
date: 2014/08/28 05:31:42;  author: root;  state: Exp;
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IPC Using SOCKETS AF_UNIX

RCS file: server.c,v
Working file: server.c
head: 1.1
branch:
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total revisions: 1;    selected revisions: 1
description:
Server implementaton using TCP , AF_UNIX.
>> Calls used : socket(), bind(), listen(), accept().
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revision 1.1
date: 2014/08/28 05:26:46;  author: root;  state: Exp;
Initial revision
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RCS file: client.c,v
Working file: client.c
head: 1.1
branch:
locks: strict
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symbolic names:
keyword substitution: kv
total revisions: 1;    selected revisions: 1
description:
AF_UXIX client program.
calls used: bind(), connect.
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revision 1.1
date: 2014/08/28 05:31:42;  author: root;  state: Exp;
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IPC USING MESSAGE QUEUES

RCS file: header.h,v
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included stdio.h, sys/msg.h, stdlib.h, sys/types.h, unistd.h, sys/ipc.h.
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revision 1.1
date: 2014/08/28 04:44:56;  author: root;  state: Exp;
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RCS file: server.c,v
Working file: server.c
head: 1.1
branch:
locks: strict
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symbolic names:
keyword substitution: kv
total revisions: 1;    selected revisions: 1
description:
this is the server program.
it creates a message queue and waits to recieve data on it from a requesting client.
multiple fork calls are made according to the number of requesting client
each child of the server deals with respective client and sychronisation chived by the type field given in each message queue structure.
then the server sends a processing requst to the processing client.
once the processing client returns the result on a seperate message queue, the server puts the result back on the respective client message queue.
each client then picks up the message according to the type specified, which in turn is their own pid(process id).
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revision 1.1
date: 2014/08/28 04:54:05;  author: root;  state: Exp;
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RCS file: client.c,v
Working file: client.c
head: 1.1
branch:
locks: strict
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symbolic names:
keyword substitution: kv
total revisions: 1;    selected revisions: 1
description:
This is the requesting client program.
It sends a request on the message queue created by the server.
and waits for the processed result.
picks up the message of its own type only.
here tpre is the pid of client.
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revision 1.1
date: 2014/08/28 05:05:52;  author: root;  state: Exp;
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RCS file: process.c,v
Working file: process.c
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description:
This is the processing client.
it performs the calculations on request from the server.
and returns the answer in a message queue created by the server.
with a particular type attached to the mesage.
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revision 1.1
date: 2014/08/28 05:08:33;  author: root;  state: Exp;
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2 RCS file: server.c,v
3 Working file: server.c
4 head: 1.2
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10 total revisions: 2; selected revisions: 2
11 description:
12 Implementation of server.
13 Protocol : TCP
14 Domain : AF_UNIX
15 —————————-
16 revision 1.2
17 date: 2014/08/25 05:19:58; author: root; state: Exp; lines: +10 -10
18 Server successfully implemented.
19 Server accepts requests and sends responses.
20 —————————-
21 revision 1.1
22 date: 2014/08/25 05:03:27; author: root; state: Exp;
23 Initial revision
24 =============================================================================
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11 total revisions: 2; selected revisions: 2
12 description:
13 implemented sockets for datagram under af_unix domain.
14 Works ok, but I have some queries.
15 Queries :
16 If more than one request come, then server’s sendto call returns bad file descriptor with each request it servers, but th e messages are exchanged properly
17 The server socket fd and the client socket fd are same, how come ?
18 —————————-
19 revision 1.2 locked by: root;
20 date: 2014/08/25 05:42:35; author: root; state: Exp; lines: +0 -6
21 Server successfully serves more than 1 client, but not simultaneoulsy, needs multithreading
22 —————————-
23 revision 1.1
24 date: 2014/08/22 20:27:03; author: root; state: Exp;
25 Initial revision
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1 line less; before #1 2 seconds ago 1,0-1 All

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12 description:
13 Implementation fo server.
14 Protocol : UDP
15 Domain : AF_INET
16 —————————-
17 revision 1.2 locked by: root;
18 date: 2014/08/25 05:13:38; author: root; state: Exp; lines: +1 -0
19 Server is able to accpet client requests and send them response.
20 Server serves one client at a time.
21 —————————-
22 revision 1.1
23 date: 2014/08/25 05:07:54; author: root; state: Exp;
24 Initial revision
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11 description:
12 Implementation of server for stream socket ( TCP ) under AF_INET domain.
13 —————————-
14 revision 1.2
15 date: 2014/08/25 04:55:04; author: root; state: Exp; lines: +1 -0
16 Server successfully implemented.
17 —————————-
18 revision 1.1
19 date: 2014/08/25 04:53:24; author: root; state: Exp;
20 Initial revision
21 =============================================================================
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RCS file: 4.2.c,v
Working file: 4.2.c
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description:
enter the 5 number and find largest and smallest number
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revision 1.1
date: 2014/08/24 06:33:38; author: root; state: Exp;
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Parallel port modes
The IEEE 1284 Standard which has been published in 1994 defines five modes of data transfer for parallel port. They are,

1) Compatibility Mode
2) Nibble Mode
3) Byte Mode
4) EPP
5) ECP

Hardware
The pin outs of DB25 connector is shown in the picture below
Parallel Port

The lines in DB25 connector are divided in to three groups, they are

1) Data lines (data bus)
2) Control lines
3) Status lines

As the name refers , data is transferred over data lines , Control lines are used to control the peripheral and of course , the peripheral returns status signals back computer through Status lines. These lines are connected to Data, Control And Status registers internally . The details of parallel port signal lines are given below
Pin No (DB25) Signal name Direction Register – bit Inverted
1 nStrobe Out Control-0 Yes
2 Data0 In/Out Data-0 No
3 Data1 In/Out Data-1 No
4 Data2 In/Out Data-2 No
5 Data3 In/Out Data-3 No
6 Data4 In/Out Data-4 No
7 Data5 In/Out Data-5 No
8 Data6 In/Out Data-6 No
9 Data7 In/Out Data-7 No
10 nAck In Status-6 No
11 Busy In Status-7 Yes
12 Paper-Out In Status-5 No
13 Select In Status-4 No
14 Linefeed Out Control-1 Yes
15 nError In Status-3 No
16 nInitialize Out Control-2 No
17 nSelect-Printer OutControl-3 Yes
18-25 Ground - - -

Parallel port registers
As you know, the Data, Control and status lines are connected to there corresponding registers inside the computer. So by manipulating these registers in program , one can easily read or write to parallel port with programming languages like ‘C’ and BASIC.

The registers found in standard parallel port are ,

1) data register
2) Status register
3) Control register

As there names specifies, Data register is connected to Data lines, Control register is connected to control lines and Status register is connected to Status lines. (Here the word connection does not mean that there is some physical connection between data/control/status lines. The registers are virtually connected to the corresponding lines.). So what ever you write to these registers , will appear in corresponding lines as voltages, Of course, you can measure it with a multimeter. And What ever you give to Parallel port as voltages can be read from these registers(with some restrictions). For example , if we write ’1′ to Data register , the line Data0 will be driven to +5v. Just like this ,we can programmatically turn on and off any of the data lines and Control lines.

RCS file: 1.c,v
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revision 1.1 locked by: root;
date: 2014/08/19 12:34:16; author: root; state: Exp;
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ret_msnd = msgsnd(ret_mget, &m_p, sizeof(struct content), 0);
89 if(strcmp(m_p.con.msg, “exit”) == 10)
90 {
91 printf(“Client 1 says bye\n”);
92 kill(pid, SIGINT); /* kill the child generated for reading the inbox, before parent goe s off */
93 exit(EXIT_SUCCESS);
94 }
95 if(ret_msnd == -1) /* msgsnd fails then kill the child , and the parent.*/
96 {
97 printf(“Failed to send message to write q\n”);
98 perror(“msgsnd”);
99 kill(pid, SIGINT);
100 exit(EXIT_FAILURE);
101 }