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Adds TCP/IP stuff

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Brendan Haines 2015-01-09 13:21:07 -07:00
parent 6276473f88
commit 7b862ad270
18 changed files with 552 additions and 380 deletions
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410
IMU/I2Cdev.h
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@ -1,4 +1,4 @@
// I2Cdev library collection - Main I2C device class
// I2Cdev library collection - Main I2C device class header file
// Abstracts bit and byte I2C R/W functions into a convenient class
// 6/9/2012 by Jeff Rowberg <jeff@rowberg.net>
//
@ -41,387 +41,37 @@ THE SOFTWARE.
===============================================
*/
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/i2c-dev.h>
#include "I2Cdev.h"
#ifndef _I2CDEV_H_
#define _I2CDEV_H_
/** Default constructor.
*/
I2Cdev::I2Cdev() {
}
#ifndef TRUE
#define TRUE (1==1)
#define FALSE (0==1)
#endif
/** Read a single bit from an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to read from
* @param bitNum Bit position to read (0-7)
* @param data Container for single bit value
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Status of read operation (true = success)
*/
int8_t I2Cdev::readBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t *data, uint16_t timeout) {
uint8_t b;
uint8_t count = readByte(devAddr, regAddr, &b, timeout);
*data = b & (1 << bitNum);
return count;
}
class I2Cdev {
public:
I2Cdev();
static int8_t readBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readByte(uint8_t devAddr, uint8_t regAddr, uint8_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readWord(uint8_t devAddr, uint8_t regAddr, uint16_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t *data, uint16_t timeout=I2Cdev::readTimeout);
static int8_t readWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t *data, uint16_t timeout=I2Cdev::readTimeout);
/** Read a single bit from a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to read from
* @param bitNum Bit position to read (0-15)
* @param data Container for single bit value
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Status of read operation (true = success)
*/
int8_t I2Cdev::readBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t *data, uint16_t timeout) {
uint16_t b;
uint8_t count = readWord(devAddr, regAddr, &b, timeout);
*data = b & (1 << bitNum);
return count;
}
static bool writeBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t data);
static bool writeBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t data);
static bool writeBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t data);
static bool writeBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t data);
static bool writeByte(uint8_t devAddr, uint8_t regAddr, uint8_t data);
static bool writeWord(uint8_t devAddr, uint8_t regAddr, uint16_t data);
static bool writeBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t *data);
static bool writeWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t *data);
/** Read multiple bits from an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to read from
* @param bitStart First bit position to read (0-7)
* @param length Number of bits to read (not more than 8)
* @param data Container for right-aligned value (i.e. '101' read from any bitStart position will equal 0x05)
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Status of read operation (true = success)
*/
int8_t I2Cdev::readBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t *data, uint16_t timeout) {
// 01101001 read byte
// 76543210 bit numbers
// xxx args: bitStart=4, length=3
// 010 masked
// -> 010 shifted
uint8_t count, b;
if ((count = readByte(devAddr, regAddr, &b, timeout)) != 0) {
uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
b &= mask;
b >>= (bitStart - length + 1);
*data = b;
}
return count;
}
/** Read multiple bits from a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to read from
* @param bitStart First bit position to read (0-15)
* @param length Number of bits to read (not more than 16)
* @param data Container for right-aligned value (i.e. '101' read from any bitStart position will equal 0x05)
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Status of read operation (1 = success, 0 = failure, -1 = timeout)
*/
int8_t I2Cdev::readBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t *data, uint16_t timeout) {
// 1101011001101001 read byte
// fedcba9876543210 bit numbers
// xxx args: bitStart=12, length=3
// 010 masked
// -> 010 shifted
uint8_t count;
uint16_t w;
if ((count = readWord(devAddr, regAddr, &w, timeout)) != 0) {
uint16_t mask = ((1 << length) - 1) << (bitStart - length + 1);
w &= mask;
w >>= (bitStart - length + 1);
*data = w;
}
return count;
}
/** Read single byte from an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to read from
* @param data Container for byte value read from device
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Status of read operation (true = success)
*/
int8_t I2Cdev::readByte(uint8_t devAddr, uint8_t regAddr, uint8_t *data, uint16_t timeout) {
return readBytes(devAddr, regAddr, 1, data, timeout);
}
/** Read single word from a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to read from
* @param data Container for word value read from device
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Status of read operation (true = success)
*/
int8_t I2Cdev::readWord(uint8_t devAddr, uint8_t regAddr, uint16_t *data, uint16_t timeout) {
return readWords(devAddr, regAddr, 1, data, timeout);
}
/** Read multiple bytes from an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr First register regAddr to read from
* @param length Number of bytes to read
* @param data Buffer to store read data in
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Number of bytes read (-1 indicates failure)
*/
int8_t I2Cdev::readBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t *data, uint16_t timeout) {
int8_t count = 0;
int fd = open("/dev/i2c-1", O_RDWR);
if (fd < 0) {
fprintf(stderr, "Failed to open device: %s\n", strerror(errno));
return(-1);
}
if (ioctl(fd, I2C_SLAVE, devAddr) < 0) {
fprintf(stderr, "Failed to select device: %s\n", strerror(errno));
close(fd);
return(-1);
}
if (write(fd, &regAddr, 1) != 1) {
fprintf(stderr, "Failed to write reg: %s\n", strerror(errno));
close(fd);
return(-1);
}
count = read(fd, data, length);
if (count < 0) {
fprintf(stderr, "Failed to read device(%d): %s\n", count, ::strerror(errno));
close(fd);
return(-1);
} else if (count != length) {
fprintf(stderr, "Short read from device, expected %d, got %d\n", length, count);
close(fd);
return(-1);
}
close(fd);
return count;
}
/** Read multiple words from a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr First register regAddr to read from
* @param length Number of words to read
* @param data Buffer to store read data in
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Number of words read (0 indicates failure)
*/
int8_t I2Cdev::readWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t *data, uint16_t timeout) {
int8_t count = 0;
printf("ReadWords() not implemented\n");
// Use readBytes() and potential byteswap
*data = 0; // keep the compiler quiet
return count;
}
/** write a single bit in an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to write to
* @param bitNum Bit position to write (0-7)
* @param value New bit value to write
* @return Status of operation (true = success)
*/
bool I2Cdev::writeBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t data) {
uint8_t b;
readByte(devAddr, regAddr, &b);
b = (data != 0) ? (b | (1 << bitNum)) : (b & ~(1 << bitNum));
return writeByte(devAddr, regAddr, b);
}
/** write a single bit in a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to write to
* @param bitNum Bit position to write (0-15)
* @param value New bit value to write
* @return Status of operation (true = success)
*/
bool I2Cdev::writeBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t data) {
uint16_t w;
readWord(devAddr, regAddr, &w);
w = (data != 0) ? (w | (1 << bitNum)) : (w & ~(1 << bitNum));
return writeWord(devAddr, regAddr, w);
}
/** Write multiple bits in an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to write to
* @param bitStart First bit position to write (0-7)
* @param length Number of bits to write (not more than 8)
* @param data Right-aligned value to write
* @return Status of operation (true = success)
*/
bool I2Cdev::writeBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t data) {
// 010 value to write
// 76543210 bit numbers
// xxx args: bitStart=4, length=3
// 00011100 mask byte
// 10101111 original value (sample)
// 10100011 original & ~mask
// 10101011 masked | value
uint8_t b;
if (readByte(devAddr, regAddr, &b) != 0) {
uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
data <<= (bitStart - length + 1); // shift data into correct position
data &= mask; // zero all non-important bits in data
b &= ~(mask); // zero all important bits in existing byte
b |= data; // combine data with existing byte
return writeByte(devAddr, regAddr, b);
} else {
return false;
}
}
/** Write multiple bits in a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to write to
* @param bitStart First bit position to write (0-15)
* @param length Number of bits to write (not more than 16)
* @param data Right-aligned value to write
* @return Status of operation (true = success)
*/
bool I2Cdev::writeBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t data) {
// 010 value to write
// fedcba9876543210 bit numbers
// xxx args: bitStart=12, length=3
// 0001110000000000 mask byte
// 1010111110010110 original value (sample)
// 1010001110010110 original & ~mask
// 1010101110010110 masked | value
uint16_t w;
if (readWord(devAddr, regAddr, &w) != 0) {
uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
data <<= (bitStart - length + 1); // shift data into correct position
data &= mask; // zero all non-important bits in data
w &= ~(mask); // zero all important bits in existing word
w |= data; // combine data with existing word
return writeWord(devAddr, regAddr, w);
} else {
return false;
}
}
/** Write single byte to an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register address to write to
* @param data New byte value to write
* @return Status of operation (true = success)
*/
bool I2Cdev::writeByte(uint8_t devAddr, uint8_t regAddr, uint8_t data) {
return writeBytes(devAddr, regAddr, 1, &data);
}
/** Write single word to a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register address to write to
* @param data New word value to write
* @return Status of operation (true = success)
*/
bool I2Cdev::writeWord(uint8_t devAddr, uint8_t regAddr, uint16_t data) {
return writeWords(devAddr, regAddr, 1, &data);
}
/** Write multiple bytes to an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr First register address to write to
* @param length Number of bytes to write
* @param data Buffer to copy new data from
* @return Status of operation (true = success)
*/
bool I2Cdev::writeBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t* data) {
int8_t count = 0;
uint8_t buf[128];
int fd;
if (length > 127) {
fprintf(stderr, "Byte write count (%d) > 127\n", length);
return(FALSE);
}
fd = open("/dev/i2c-1", O_RDWR);
if (fd < 0) {
fprintf(stderr, "Failed to open device: %s\n", strerror(errno));
return(FALSE);
}
if (ioctl(fd, I2C_SLAVE, devAddr) < 0) {
fprintf(stderr, "Failed to select device: %s\n", strerror(errno));
close(fd);
return(FALSE);
}
buf[0] = regAddr;
memcpy(buf+1,data,length);
count = write(fd, buf, length+1);
if (count < 0) {
fprintf(stderr, "Failed to write device(%d): %s\n", count, ::strerror(errno));
close(fd);
return(FALSE);
} else if (count != length+1) {
fprintf(stderr, "Short write to device, expected %d, got %d\n", length+1, count);
close(fd);
return(FALSE);
}
close(fd);
return TRUE;
}
/** Write multiple words to a 16-bit device register.
* @param devAddr I2C slave device address
* @param regAddr First register address to write to
* @param length Number of words to write
* @param data Buffer to copy new data from
* @return Status of operation (true = success)
*/
bool I2Cdev::writeWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t* data) {
int8_t count = 0;
uint8_t buf[128];
int i, fd;
// Should do potential byteswap and call writeBytes() really, but that
// messes with the callers buffer
if (length > 63) {
fprintf(stderr, "Word write count (%d) > 63\n", length);
return(FALSE);
}
fd = open("/dev/i2c-1", O_RDWR);
if (fd < 0) {
fprintf(stderr, "Failed to open device: %s\n", strerror(errno));
return(FALSE);
}
if (ioctl(fd, I2C_SLAVE, devAddr) < 0) {
fprintf(stderr, "Failed to select device: %s\n", strerror(errno));
close(fd);
return(FALSE);
}
buf[0] = regAddr;
for (i = 0; i < length; i++) {
buf[i*2+1] = data[i] >> 8;
buf[i*2+2] = data[i];
}
count = write(fd, buf, length*2+1);
if (count < 0) {
fprintf(stderr, "Failed to write device(%d): %s\n", count, ::strerror(errno));
close(fd);
return(FALSE);
} else if (count != length*2+1) {
fprintf(stderr, "Short write to device, expected %d, got %d\n", length+1, count);
close(fd);
return(FALSE);
}
close(fd);
return TRUE;
}
/** Default timeout value for read operations.
* Set this to 0 to disable timeout detection.
*/
uint16_t I2Cdev::readTimeout = 0;
static uint16_t readTimeout;
};
#endif /* _I2CDEV_H_ */

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all: TCPserver.o TCPserverExample
HDRS = TCPserver.h
CXXFLAGS = -Wall
TCPserver.o TCPserverExample.o: $(HDRS)
TCPserverExample: TCPserver.o TCPserverExample.o
$(CXX) $^ -o $@
clean:
rm TCPserver.o TCPserverExample.o TCPserverExample

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/**
* TCPclient.java
* Written by Brendan Haines
* Based on example from http://www.java-samples.com/showtutorial.php?tutorialid=1167
*/
import java.lang.*;
import java.io.*;
import java.net.*;
class TCPclient {
/** Socket at the server */
private Socket socket;
/** buffer to hold received info */
private BufferedReader buffer;
/**
* Connects to socket at server
* @param host - the server's IP
* @param port - the port number of the socket at the server
*/
public TCPclient( String host, int port ) {
try {
System.out.println( "setting up socket" );
socket = new Socket( host, port );
System.out.println( "socket set up\nsetting up buffer" );
buffer = new BufferedReader( new InputStreamReader( socket.getInputStream() ) );
System.out.println( "buffer set up" );
}
catch( Exception e ) {
System.out.println( "ERROR -- constructor" );
close();
}
}
/**
* reads one line from the receive buffer
* @return one line of the receive buffer on success, null on failure
*/
public String readLine() {
try{
if( buffer.ready() ) {
return buffer.readLine();
}
else {
return null;
}
}
catch( Exception e ) {
System.out.println( "Hmmm... it won't read" );
return null;
}
}
/**
* close connection
*/
public void close() {
try {
buffer.close();
socket.close();
}
catch( Exception e ) {
System.out.println( "SH*T! the connection won't close" );
}
}
}

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/**
* Written By Brendan Haines
*/
class TCPclientExample {
public static void main( String args[] ) {
TCPclient client = new TCPclient( "192.168.42.1", 51719 );
System.out.println( "Setup successful" );
client.close();
}
}

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/*
* TCPserver.cpp
* Written by Brendan Haines
* Based heavily on example code found at http://www.linuxhowtos.org/C_C++/socket.htm
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <pthread.h>
#include "TCPserver.h"
TCPserver::TCPserver()
{}
// Constructor sets everything up and starts monitoring thread
TCPserver::TCPserver( int port )
{
portNumber = port;
setupSocket();
}
// Destructor closes sockets
TCPserver::~TCPserver()
{
close( connectionFD );
close( socketFD );
}
// a unified/consistent way of reporting errors
void TCPserver::handleError( const char* message )
{
perror( message ); // print message to stderror
}
// Returns true on success, false on failure
bool TCPserver::setupSocket()
{
// Create a new socket
// AF_INET: internet domain (not unix domain)
// SOCK_STREAM: stream (not datagram)
// 0: lets OS decide correct protocol (TCP)
socketFD = socket( AF_INET, SOCK_STREAM, 0 );
if( socketFD < 0 ) // error setting up socket
{
handleError( "Error setting up socket\n" );
return false;
}
// fill server_addr with zeroes
// NOTE: memset sets arg2 bytes following arg0 to arg1
// NOTE: sizeof returns the size of the passed type in bytes
memset( (char*) &server_addr, 0, sizeof( server_addr ) );
server_addr.sin_family = AF_INET; // just following the example (and its documentation)
server_addr.sin_port = htons( portNumber ); // assign the port number. NOTE: htons converts host byte order to network byte order
server_addr.sin_addr.s_addr = INADDR_ANY; // INADDR_ANY represents the IP address of the host
// bind: binds the socket to an address
if( bind( socketFD, (struct sockaddr*) &server_addr, sizeof( server_addr ) ) < 0 )
{
handleError( "Error binding socket" );
return false;
}
// listen for connections to socket (max 5 waiting)
listen( socketFD, 5 );
clientAddrLen = sizeof( client_addr );
// wait for client to connect
printf( "Waiting for client to connect\n" );
connectionFD = accept( socketFD, (struct sockaddr*) &client_addr, &clientAddrLen );
if( connectionFD < 0 )
{
handleError( "Error on accept" );
return false;
}
// empty buffer
memset( buffer, 0, sizeof( buffer ) );
return true; // setup successful
}
// returns a pointer to the buffer
char* TCPserver::getBuffer()
{
return buffer;
}
// returns the connection file descriptor
int TCPserver::getConnectionFD()
{
return connectionFD;
}
/*
void TCPserver::startMonitoringThread()
{
// create thread: ( thread, NULL = default values, function to run, parameter (void*) or NULL )
if( pthread_create( &monitorThread, NULL, monitoringThread, (void*) this ) )
{
// error creating thread
handleError( "Error creating thread" );
return;
}
}
void* TCPserver::monitoringThread( void* serverPointer )
{
int n; // contains the number of characters read
TCPserver server;
while( true )
{
// read from the socket and put in the buffer
n = read( server.getConnectionFD(), server.getBuffer(), 255 );
if( n < 0 )
{
server.handleError( "Error reading -- monitorThread " );
pthread_exit( NULL ); // exit this thread
}
}
}
*/

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/*
* TCPserver.h
* Written by Brendan Haines
* Based heavily on example code found at http://www.linuxhowtos.org/C_C++/socket.htm
*/
#ifndef TCP_SERVER_H
#define TCP_SERVER_H
#include <netinet/in.h>
class TCPserver {
public:
TCPserver();
TCPserver( int port ); // Constructor
~TCPserver(); // Destructor
void handleError( const char* message );
char* getBuffer();
int getConnectionFD();
char buffer[ 256 ]; // buffer to store read data
private:
int socketFD; // file descriptor for the socket
int connectionFD; // file descriptor for the connection
int portNumber; // port number of the socket
socklen_t clientAddrLen; // stores the length of the client's address
struct sockaddr_in server_addr; // contains the server's address
struct sockaddr_in client_addr; // contains the client's address
//pthread_t monitorThread; // thread to monitor the socket and read to buffer
bool setupSocket();
//void startMonitoringThread();
//void* monitoringThread( void* );
};
#endif

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/*
* TCPserverExample.cpp
*/
#include "stdio.h"
#include "TCPserver.h"
int main( int argc, char* argv[] )
{
TCPserver serv( 51719 );
}

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Example code using TCP/IP protocol with C++
Example and documentation found at http://www.linuxhowtos.org/C_C++/socket.htm
server.c and client.c are original files
server2.c is commented and reformatted to facilitate understanding the underlying process

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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
void error(const char *msg)
{
perror(msg);
exit(0);
}
int main(int argc, char *argv[])
{
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[256];
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0);
}
portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,
(char *)&serv_addr.sin_addr.s_addr,
server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
error("ERROR connecting");
printf("Please enter the message: ");
bzero(buffer,256);
fgets(buffer,255,stdin);
n = write(sockfd,buffer,strlen(buffer));
if (n < 0)
error("ERROR writing to socket");
bzero(buffer,256);
n = read(sockfd,buffer,255);
if (n < 0)
error("ERROR reading from socket");
printf("%s\n",buffer);
close(sockfd);
return 0;
}

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/* A simple server in the internet domain using TCP
The port number is passed as an argument */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
void error(const char *msg)
{
perror(msg);
exit(1);
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno;
socklen_t clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0)
error("ERROR on binding");
listen(sockfd,5);
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,
(struct sockaddr *) &cli_addr,
&clilen);
if (newsockfd < 0)
error("ERROR on accept");
bzero(buffer,256);
n = read(newsockfd,buffer,255);
if (n < 0) error("ERROR reading from socket");
printf("Here is the message: %s\n",buffer);
n = write(newsockfd,"I got your message",18);
if (n < 0) error("ERROR writing to socket");
close(newsockfd);
close(sockfd);
return 0;
}

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/* A simple server in the internet domain using TCP
The port number is passed as an argument */
// From:
// http://www.linuxhowtos.org/C_C++/socket.htm
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
void error( const char *msg )
{
perror( msg );
exit( 1 );
}
int main( int argc, char *argv[] )
{
// VARIABLE DEFINITONS
// file descriptors
int sockfd; // returned by socket system call
int newsockfd; // returned by accept system call
int portno; // stores port number (passed as argument)
socklen_t clilen; // stores the size of the client address. needed for the accept system call
char buffer[ 256 ]; // server reads characters from socket connection into buffer
// sockaddr_in is defined in "netinet/in.h"
struct sockaddr_in serv_addr; // serv_addr contains the server address
struct sockaddr_in cli_addr; // cli_addr contains the client address
int n; // return value for read/write calls (contains the # of characters read/written)
// BEGIN REAL CODE
// Check that there are enough arguments
if( argc < 2 )
{
fprintf( stderr, "ERROR, no port provided\n" );
exit( 1 );
}
// socket system call creates new socket
// arg0: address domain ( Unix domain [AF_UNIX] or Internet domain [AF_INET] )
// arg1: socket type ( Stream [SOCK_STREAM] or Datagram [SOCK_DGRAM] )
// arg2: protocol ( 0 lets system decide best protocol: TCP for streams, UDP for datagrams )
// returns file descriptor on success
// returns -1 on failure
sockfd = socket( AF_INET, SOCK_STREAM, 0 );
if( sockfd < 0 ) // on error: sockfd = -1
error( "ERROR opening socket" );
// bzero sets all values in a buffer to zero
// arg0: pointer to buffer
// arg1: length of buffer
bzero( (char*) &serv_addr, sizeof( serv_addr ) ); // initializes serv_addr to all zeroes
// atoi converts a string of digits to an integer
portno = atoi( argv[ 1 ] );
serv_addr.sin_family = AF_INET; // sin_family should always be set to symbolic constant AF_INET
serv_addr.sin_addr.s_addr = INADDR_ANY; // sin_addr.s_addr contains the IP address of the host. INADDR_ANY is a symbolic constant which get this address
serv_addr.sin_port = htons( portno ); // sin_port contains the port number. htons converts a port number in host byte order to network byte order
// bind system call binds a socket to an address ( address = address of host & port number)
// arg0: socket file descriptor
// arg1: pointer to structure of type sockaddr. what is passed is a structure of type sockaddr_in, must be cast to correct type
// arg2: size of structure &arg1
// returns 0 on success ?????????
if( bind( sockfd, ( struct sockaddr* ) &serv_addr, sizeof( serv_addr ) ) < 0 )
error( "ERROR on binding" );
// listen system call allows program to listen to socket for connections
// arg0: file descriptor of socket
// arg1: size of backlog queue (maximum number of connections which can be waiting while handling any specific connection) (standard: 5)
listen( sockfd, 5 );
// set client address length to the size of client's address
clilen = sizeof( cli_addr );
// accept system call causes the program to stop until a client connects to the server
// arg0: file descriptor of the socket
// arg1: pointer for the client address structure
// arg2: size of structure &arg1
// returns a file descriptor for the connection on success
// returns -1 on failure ?????
newsockfd = accept( sockfd, (struct sockaddr *) &cli_addr, &clilen );
if( newsockfd < 0 )
error( "ERROR on accept" );
bzero( buffer, 256 ); // clear the receive buffer
// read system call reads from socket
// read will block the program until there is something to read
// arg0: file descriptor for the connection (NOTE: this is the new one returned by accept)
// arg1: buffer to put characters into
// arg2: maximum number of character to read and put in buffer
// return number of characters read on success
// return -1 on failure ?????
n = read( newsockfd, buffer, 255 );
if ( n < 0 )
error("ERROR reading from socket");
// buffer will contain the message now
printf( "Here is the message: %s\n", buffer );
// write system call writes to socket
// arg0: file descriptor for the connection (NOTE: again, this is the new one returned by accept)
// arg1: pointer to character (char*)
// arg2: length of &arg1
// return number of characters written on success
// return -1 on failure
n = write( newsockfd, "I got your message", 18 );
if ( n < 0 )
error( "ERROR writing to socket" );
// when socket is no longer needed, close the connection
close( newsockfd );
close( sockfd );
return 0;
}