linux UDP/TCP socket programming

UDP programming:

1. Create descriptor using socket
2. Bind bind local ip address port
3. Use recvfrom to receive data
4. Send data using sendto
5. Close descriptor close(fd)

#include "stdio.h"
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <linux/net.h>
#include <arpa/inet.h>
#include "string.h"

char buffer[256];
int main(int argc,char*argv[])
{
    struct sockaddr_in socket_addr;
    struct sockaddr_in rx_addr;
    printf("%s,%d test example \n",__FILE__,__LINE__);
    int socket_fd = socket(AF_INET, SOCK_DGRAM,0);
    
    socket_addr.sin_family = AF_INET;
    socket_addr.sin_addr.s_addr = inet_addr("192.168.146.129");
    socket_addr.sin_port = htons(6451);
    int ret = bind(socket_fd,(__CONST_SOCKADDR_ARG)&socket_addr,sizeof(socket_addr));
    printf("%s,%d bind ret %d\n",__FILE__,__LINE__,ret);
    printf("%s,%d ip addr %x\n",__FILE__,__LINE__,socket_addr.sin_addr.s_addr);
    memcpy(&rx_addr,&socket_addr,sizeof(rx_addr));
    socket_addr.sin_family = AF_INET;
    socket_addr.sin_addr.s_addr = inet_addr("192.168.9.128");
    socket_addr.sin_port = htons(6001);

    int len = 0;
    ret = sendto(socket_fd,buffer,10,0,(__CONST_SOCKADDR_ARG)&socket_addr,sizeof(socket_addr));
    memset(&rx_addr,0,sizeof(rx_addr));
    while(1){
        ret=recvfrom(socket_fd,buffer,256,0,(__SOCKADDR_ARG)&rx_addr,&len);
        for(int i=0;i<256;i++){
            buffer[i] = buffer[i]+1;
        }
        printf("%s,%d recvfrom ret %d\n",__FILE__,__LINE__,ret);
        ret = sendto(socket_fd,buffer,ret,0,(__CONST_SOCKADDR_ARG)&socket_addr,sizeof(socket_addr));
        printf("%s,%d sendto ret %d\n",__FILE__,__LINE__,ret);
        printf("%d,%x\n",rx_addr.sin_port,rx_addr.sin_addr);
        // sleep(1);
       
    }
    close(socket_fd);
    return 0;
}

TCP client programming:

1. Create a data flow descriptor using a socket
2. Bind local address bind port
3. connect to client connect
4. readreceive data
5. writeSend data
6. closeClose descriptor

#include "stdio.h"
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <linux/net.h>
#include <arpa/inet.h>
#include "string.h"

#define  CLEAR(type) memset(&type,0,sizeof(type))

int main(int argc,char*argv[])
{
    printf("%s,%d test example \n",__FILE__,__LINE__);
    char buffer[256];
    int fd = socket(AF_INET,SOCK_STREAM,0);
    struct sockaddr_in addr;
    CLEAR(addr);
    addr.sin_addr.s_addr = inet_addr("192.168.126.129"); 
    addr.sin_family = AF_INET;
    addr.sin_port = htons(4567);

    int ret = bind(fd,(__CONST_SOCKADDR_ARG)&addr,sizeof(addr));
    CLEAR(addr);
    addr.sin_addr.s_addr = inet_addr("192.168.11.66"); 
    addr.sin_family = AF_INET;
    addr.sin_port = htons(6000);
    ret = connect(fd,(__CONST_SOCKADDR_ARG)&addr,sizeof(addr));
    while (1)
    {
        ret = read(fd,buffer,256);
        printf("%d,%x\n",__LINE__,ret);
        ret = write(fd,buffer,ret);
         printf("%d,%x\n",__LINE__,ret);
    }
    close(fd);
    return 0;
}

TCP server programming:

1. Create a data flow descriptor using a socket
2. Bind local address bind port
3. listenlocalport
4. accpet returns the newly created socket after waiting for a connection.
5. Use fork to create and handle new incoming connections
6. Use the socket returned by read accpect
7. Use the socket returned by write accept

#include "stdio.h"
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <linux/net.h>
#include <arpa/inet.h>
#include "string.h"

#define  CLEAR(type) memset(&type,0,sizeof(type))

int main(int argc,char*argv[])
{
    printf("%s,%d test example \n",__FILE__,__LINE__);
    char buffer[256];
    int len=0;
    int fd = socket(AF_INET,SOCK_STREAM,0);
    struct sockaddr_in addr;
    CLEAR(addr);
    addr.sin_addr.s_addr = inet_addr("192.168.146.129"); 
    addr.sin_family = AF_INET;
    addr.sin_port = htons(4567);

    int afdret = bind(fd,(__CONST_SOCKADDR_ARG)&addr,sizeof(addr));
    // CLEAR(addr);
    // addr.sin_addr.s_addr = inet_addr("192.168.11.66"); 
    // addr.sin_family = AF_INET;
    // addr.sin_port = htons(6000);
    int ret = listen(fd,5);
    int afd=0;
    while (1)
    {
        CLEAR(addr);
        afd = accept(fd,(__SOCKADDR_ARG)&addr,&len);
        if(ret!=-1){
            printf("accept %s %d\n",inet_ntoa(addr.sin_addr),len);
            if(fork()){
                while (1)
                {
                    ret = read(afd,buffer,256);
                    printf("%d,%x\n",__LINE__,ret);
                    ret = write(afd,buffer,ret);
                    printf("%d,%x\n",__LINE__,ret); /* code */
                }
                
             
            }    
        }
     
        
    }
    close(fd);
    return 0;
}

Reference material: "Linux Network Programming" Song Bin