#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <assert.h>

#include <stdio.h>

#include <unistd.h>

#include <string.h>

#include <stdlib.h>

int main( int argc, char* argv[] )

{

    if( argc <= 2 )

    {

        printf( "usage: %s ip_address port_number\n", basename( argv[0] ) );

        return 1;

    }

    const char* ip = argv[1];

    int port = atoi( argv[2] );

    struct sockaddr_in server_address;

    bzero( &server_address, sizeof( server_address ) );

    server_address.sin_family = AF_INET;

    inet_pton( AF_INET, ip, &server_address.sin_addr );

    server_address.sin_port = htons( port );

    int sockfd = socket( PF_INET, SOCK_STREAM, 0 );

    assert( sockfd >= 0 );

    if ( connect( sockfd, ( struct sockaddr* )&server_address, sizeof( server_address ) ) < 0 )

    {

        printf( "connection failed\n" );

    }

    else

    {

        printf( "send oob data out\n" );

        const char* oob_data = "abc";

        const char* normal_data = "123";

        send( sockfd, normal_data, strlen( normal_data ), 0 );

        send( sockfd, oob_data, strlen( oob_data ), MSG_OOB );

        send( sockfd, normal_data, strlen( normal_data ), 0 );

    }

    close( sockfd );

    return 0;

}

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <assert.h>

#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#define BUF_SIZE 1024

int main( int argc, char* argv[] )

{

    if( argc <= 2 )

    {

        printf( "usage: %s ip_address port_number\n", basename( argv[0] ) );

        return 1;

    }

    const char* ip = argv[1];

    int port = atoi( argv[2] );

    struct sockaddr_in address;

    bzero( &address, sizeof( address ) );

    address.sin_family = AF_INET;

    inet_pton( AF_INET, ip, &address.sin_addr );

    address.sin_port = htons( port );

    int sock = socket( PF_INET, SOCK_STREAM, 0 );

    assert( sock >= 0 );

    int ret = bind( sock, ( struct sockaddr* )&address, sizeof( address ) );

    assert( ret != -1 );

    ret = listen( sock, 5 );

    assert( ret != -1 );

    struct sockaddr_in client;

    socklen_t client_addrlength = sizeof( client );

    int connfd = accept( sock, ( struct sockaddr* )&client, &client_addrlength );

    if ( connfd < 0 )

    {

        printf( "errno is: %d\n", errno );

    }

    else

    {

        char buffer[ BUF_SIZE ];

        memset( buffer, '\0', BUF_SIZE );

        ret = recv( connfd, buffer, BUF_SIZE-1, 0 );

        printf( "got %d bytes of normal data '%s'\n", ret, buffer );

        memset( buffer, '\0', BUF_SIZE );

        ret = recv( connfd, buffer, BUF_SIZE-1, MSG_OOB );

        printf( "got %d bytes of oob data '%s'\n", ret, buffer );

        memset( buffer, '\0', BUF_SIZE );

        ret = recv( connfd, buffer, BUF_SIZE-1, 0 );

        printf( "got %d bytes of normal data '%s'\n", ret, buffer );

        close( connfd );

    }

    close( sock );

    return 0;

}