#include <sys/scoket.h>
int getsockopt ( int sockfd, int level, int option_name, void* option_value, socklen_t* restrict option_len );
int setsockopt ( int sockfd, int level, int option_name, const void* option_value, socklen_t option_len);

#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>
 
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] );
 
  int sock = socket( PF_INET, SOCK_STREAM, 0 );
  assert( sock >= 0 );
  int reuse = 1;
  setsockopt( sock, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof( reuse ) );
 
  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 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 remote[INET_ADDRSTRLEN ];
    printf( "connected with ip: %s and port: %d\n", 
      inet_ntop( AF_INET, &client.sin_addr, remote, INET_ADDRSTRLEN ), ntohs( client.sin_port ) );
    close( connfd );
  }
 
  close( sock );
  return 0;
}

#include <sys/socket.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
 
#define BUFFER_SIZE 512
 
int main( int argc, char* argv[] )
{
  if( argc <= 3 )
  {
    printf( "usage: %s ip_address port_number send_bufer_size\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 sock = socket( PF_INET, SOCK_STREAM, 0 );
  assert( sock >= 0 );
 
  int sendbuf = atoi( argv[3] );
  int len = sizeof( sendbuf );
  setsockopt( sock, SOL_SOCKET, SO_SNDBUF, &sendbuf, sizeof( sendbuf ) );
  getsockopt( sock, SOL_SOCKET, SO_SNDBUF, &sendbuf, ( socklen_t* )&len );
  printf( "the tcp send buffer size after setting is %d\n", sendbuf );
 
  if ( connect( sock, ( struct sockaddr* )&server_address, sizeof( server_address ) ) != -1 )
  {
    char buffer[ BUFFER_SIZE ];
    memset( buffer, 'a', BUFFER_SIZE );
    send( sock, buffer, BUFFER_SIZE, 0 );
  }
 
  close( sock );
  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 BUFFER_SIZE 1024
 
int main( int argc, char* argv[] )
{
  if( argc <= 3 )
  {
    printf( "usage: %s ip_address port_number receive_buffer_size\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 recvbuf = atoi( argv[3] );
  int len = sizeof( recvbuf );
  setsockopt( sock, SOL_SOCKET, SO_RCVBUF, &recvbuf, sizeof( recvbuf ) );
  getsockopt( sock, SOL_SOCKET, SO_RCVBUF, &recvbuf, ( socklen_t* )&len );
  printf( "the receive buffer size after settting is %d\n", recvbuf );
 
  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[ BUFFER_SIZE ];
    memset( buffer, '\0', BUFFER_SIZE );
    while( recv( connfd, buffer, BUFFER_SIZE-1, 0 ) > 0 ){}
    close( connfd );
  }
 
  close( sock );
  return 0;
}

#include <sys/socket.h>
struct linger
{
  int l_onoff; //開(kāi)啟（非0）還是關(guān)閉（0）該選項(xiàng)
  int l_linger; // 滯留時(shí)間
};