The experiment __arduino of network programming under Linux

(1) TCP programming

Server-Side TCP_SERVER.C

#include  <stdlib.h>   #include  <stdio.h>   #include  <errno.h >   #include  <string.h>   #include  <netdb.h>   #include  <sys/types.h>   #include  <netinet/in.h>   #include  <sys/ socket.h>     #define  portnumber 3333    Int main (int argc,  Char *argv[])    {       int sockfd,new_fd;        struct sockaddr_in server_addr;       struct  sockaddr_in client_addr;       int sin_size;        int nbytes;      char buffer[1024];               /*  server-side starts to establish SOCKFD descriptor  */        if ((SOCKFD=socket (af_inet,sock_stream,0)) ==-1)  // AF_INET:IPV4; sock_stream:tcp      {            fprintf (stderr, "Socket error:%s\n\a", Strerror (errno));            exit (1);       }         /*  Server-side filled &NBSP;SOCKADDR structure  */       bzero (&server_addr,sizeof struct  SOCKADDR_IN); //  initialization, placing 0      server_addr.sin_family=AF_INET;                  // internet   &NBSP;&NBSP;&NBSP;&NBSP;SERVER_ADDR.SIN_ADDR.S_ADDR=HTONL (Inaddr_any);  //  ( Converts long data on this machine to long data on the network and any host communication   //INADDR_ANY  indicates that data that can receive any IP address is bound to all ip     &NBSP;&NBSP;//SERVER_ADDR.SIN_ADDR.S_ADDR=INET_ADDR ("192.168.1.1");   //forBinding to a fixed ip,inet_addr for converting digitally formatted IP into a plastic ip      server_addr.sin_port=htons (portnumber);          //  (convert short data on this machine to short data on the network) port number              /*  Bundle SOCKFD Descriptor to IP address  */        if (Bind (SOCKFD, (struct sockaddr *) (&server_addr), sizeof (STRUCT&NBSP;SOCKADDR)) ==-1)         {           fprintf (stderr, " Bind error:%s\n\a ", Strerror (errno));           exit (1);        }         /*  set maximum number of clients allowed to connect  */        if (Listen (sockfd,5) ==-1)        {           fprintf (stderr, "Listen error:%s\n\a", Strerror (errno));    &NBSp;       exit (1);       }         while (1)        {            /*  server is blocked until client program establishes the connection  */            sin_size=sizeof (struct sockaddr_in);           if ( (New_fd=accept (SOCKFD, (struct sockaddr *) (&AMP;CLIENT_ADDR), &sin_size)) ==-1)             {                fprintf (stderr, "Accept error:%s\n\a", Strerror (errno));                exit (1);            }           fprintf (stderr, "server get  connection&Nbsp;from %s\n ", Inet_ntoa (CLIENT_ADDR.SIN_ADDR); //  translates network addresses into. String                      if (Nbytes=read (New_fd,buffer, 1024) ==-1)            {                fprintf (stderr, "read error:%s\n", Strerror (errno));                exit (1);            }                  buffer[nbytes]= ';  '         printf (" Server received %s\n ", buffer);                     /*  This newsletter is over  */           &nbSp;close (NEW_FD);           /*  cycle Next  */       }         /*  End Newsletter  */        close (SOCKFD);       exit (0);  }    

Client tcp_client.c

#include  <stdlib.h>   #include  <stdio.h>   #include  <errno.h >   #include  <string.h>   #include  <netdb.h>   #include  <sys/types.h>   #include  <netinet/in.h>   #include  <sys/ socket.h>     #define  portnumber 3333    Int main (int argc,  Char *argv[])    {       int sockfd;        char buffer[1024];       struct sockaddr_in server_ addr;       struct hostent *host;              /*  use hostname query host  name  */      if (argc!=2 )        {           fprintf ( stderr, "UsaGe:%s hostname \a\n ", argv[0]);           exit (1);        }         if (Host=gethostbyname (argv[1)) )        {            ==null) fprintf (stderr, "gethostname error\n");           exit (1) ;       }         /*  client program started to set up   SOCKFD Descriptor  */       if ((Sockfd=socket (af_inet,sock_stream,0)) ==-1)  //  AF_INET:Internet; sock_stream:tcp      {            fprintf (stderr, "socket error:%s\a\n", Strerror (errno));            exit (1);       }         /*  Client programs populate service-side information  */       bzero (&server_addr,sizeof (SERVER_ADDR));  //   initialization, placing 0      server_addr.sin_family=AF_INET;           // IPV4      server_addr.sin_port=htons (portnumber);   //  (convert short data on this machine to short data on the network) port number       server_addr.sin_addr=* ( struct in_addr *) host->h_addr);  // ip address              /*  Client initiated connection request  */       if (SOCKFD, struct  sockaddr *) (&AMP;SERVER_ADDR), sizeof (STRUCT&NBSP;SOCKADDR)) ==-1)        {            fprintf (stderr, "connect error:%s\a\n", Strerror (errno));           exit (1);        }        /*  Connection succeeded  */       printf ("please  input char:\n ");            /*  send data  */      fgets (Buffer,1024,stdin);       write (Sockfd,buffer, strlen (buffer);         /*  End Newsletter  */        close (SOCKFD);       exit (0);  }  

(2) UDP programming

Server-Side UDP_SERVER.C

#include  <stdlib.h>  #include  <stdio.h>  #include  <errno.h>  # include <string.h>  #include  <unistd.h>  #include  <netdb.h>  # include <sys/socket.h>  #include  <netinet/in.h>  #include  <sys/types.h >  #include  <arpa/inet.h>    #define  SERVER_PORT 8888   #define  MAX_MSG_SIZE 1024     Void udps_respon (INT&NBSP;SOCKFD)    {       struct sockaddr_in addr;       int addrlen ,n;       char msg[MAX_MSG_SIZE];          while (1)        {   /*  read from the network and write to the network  */            bzero (msg,sizeof (msg)); //  initialization, clear 0           addrlen = sizeof (struct sockaddr);            n=recvfrom (sockfd,msg,max_msg_size,0, struct sockaddr*) &addr,& Addrlen); //  receive messages from the client           msg[n]=0;           /*  Display Server has received information  */            fprintf (stdout, "server have received %s", msg); //  display message       }  }     int main (void)    {       int sockfd;       struct sockaddr_in addr;          /*  server-side start to build socket descriptor  */        sockfd=socket (af_inet,sock_dgram,0);       if (sockfd<0)         {           fprintf (stderr, "socket error:%s\n", Strerror ( errno);           exit (1);        }         /*  server-side fill  sockaddr architecture  */        bzero (&addr,sizeof (struct sockaddr_in));        addr.sin_family=af_inet;       addr.sin_addr.s_addr=htonl (INADDR_ANY);        addr.sin_port=htons (server_port);         /*   Bundle SOCKFD Descriptor  */       if (Bind sockfd, (struct sockaddr *) & Addr,sizeof (struct sockaddr_in) <0)        {            fprintf (stderr, "bind error:%s\n", Strerror (errno));         &Nbsp;  exit (1);       }         udps_ Respon (SOCKFD); //  for read-write operations       close (SOCKFD);  }  

Client udp_client.c

#include  <stdlib.h>  #include  <stdio.h>  #include  <errno.h>  # include <string.h>  #include  <unistd.h>  #include  <netdb.h>  # include <sys/socket.h>  #include  <netinet/in.h>  #include  <sys/types.h >  #include  <arpa/inet.h>    #define  SERVER_PORT 8888   #define  MAX_BUF_SIZE 1024     Void udpc_requ (int sockfd,const struct  Sockaddr_in *addr,int len)    {       char buffer[max_buf_ size];       int n;       while (1)        {   /*  read from keyboard, write to service side  */            printf ("please input char:\n");            fgets (Buffer,max_buf_size,stdin);           sendto (SOCKFD, Buffer,strlen (buffer), 0,addr,len);           bzero (Buffer,MAX _buf_size);       }  }     Int main (INT&NBSP;ARGC, CHAR&NBSP;**ARGV)    {       int sockfd;        struct sockaddr_in addr;         if (argc!=2)         {           fprintf (stderr, " Usage:%s server_ip\n ", argv[0]);           exit (1);        }        /*  establish &NBSP;SOCKFD descriptor  */        sockfd=socket (af_inet,sock_dgram,0);       if ( sockfd<0)        {           fprintf (stderr, " Socket error:%s\n ", Strerror (errno));           exit (1);        }         /*  filling service-side information  */        bzero (&addr,sizeof (struct sockaddr_in));        addr.sin_family=AF_INET;       addr.sin_port=htons (Server_port);      if (Inet_aton (argv[1],&addr.sin_addr) <0)   /*inet_ The Aton function is used to convert a string-type IP address into a network 2 digital */       {            fprintf (stderr, "ip error:%s\n", Strerror (errno));            exit (1);       }          udpc_requ (sockfd,&addr,sIzeof (struct sockaddr_in)); //  for read-write operations       close (SOCKFD);  }   

(3) Concurrent server design (TCP needs to establish a connection, so for the loop server, by creating a subprocess fork () to implement; UDP can be concurrent)

Server-side tcp_server_fork.c, client ditto

#include <stdlib.h> #include <stdio.h> #include <errno.h>&