The sticky packet problem of TCP and the non-boundary of data

Service side:

#include  <stdio.h> #include  <winsock2.h> #pragma  comment  (lib,  "Ws2_32.lib" )   //load  ws2_32.dll  #define  buf_size 100 int main (int argc,  Char *argv[]) {    //initialization  DLL    WSADATA wsaData;     wsastartup ( makeword (2, 2),  &wsadata);       //Create socket     socket servsock = socket (pf_inet, sock_stream,  IPPROTO_TCP);     if (Servsock == invalid_socket)     {         printf ("Failed socket (). \ n");         wsacleanup ();        return 0;     }      //binding Sockets     struct sockaddr_in  Sockaddr;   &nbsP;memset (&sockaddr, 0, sizeof (sockaddr))   //each byte is filled with 0      sockaddr.sin_family = pf_inet;  //using IPV4 address     sockaddr.sin_addr.s_addr &NBSP;=&NBSP;INET_ADDR ("127.0.0.1");   //specific IP address     sockaddr.sin_port =  htons (1234);   //Port     if (Bind (servsock,  (sockaddr*) &sockAddr,  sizeof (SOCKADDR))  == socket_error)     {         printf ("Failed bind (). \ n");         wsacleanup () ;        return 0;    }       //into the Listening state     listen (SERVSOCK,&NBSP;20);       //loop receive client request     int nsize = sizeof (SOCKADDR);     char buffer[buf_size];//Buffer      sockaddr clntaddr;    socket clntsock;           for (;;)     {        clntsock = accept (ServSock,   (sockaddr*) &clntaddr, &nsize);         sleep (10000) ;//Note here, let the program pause for 10 seconds                 &NBSP;&NBSP;INT&NBSP;STRLEN&NBSP;=&NBSP;RECV (clntsock, buffer, buf_size, 0);//Receive data from clients                    if ( Clntsock == invalid_socket)         {             printf ("failed accept (). \ n");             continue;        }        //send the client data back to           send (clntsock, buffer, strlen, 0);                  memset (buffer, 0, buf_size);// Set Buffer                    //Close Socket         closesocket (clntsock);     }       //Close Socket     closesocket (servsock);       //Termination  DLL  Use     wsacleanup ();       return 0;}

Client:

#include  <stdio.h> #include  <stdlib.h> #include  <winsock2.h> #pragma   Comment (lib,  "ws2_32.lib") #define  buf_size 100 int main (Int argc, char  *agrv[]) {    //initialization dll    wsadata wsadata;     wsastartup (Makeword (2,2),  &wsadata);           for (;;)     {             //Creating sockets         socket sock = socket (PF_INET, SOCK_STREAM, &NBSP;IPPROTO_TCP);         if (Sock == invalid_socket)          {             printf ("Failed socket (). \ n");             wsacleanup ();            return 0;         }              / /initiate a request to the server         struct sockaddr_in sockAddr;         memset (&sockaddr, 0, sizeof (SOCKADDR));  //each byte is populated with 0         sockAddr.sin_family = PF_INET;    &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;SOCKADDR.SIN_ADDR.S_ADDR&NBSP;=&NBSP;INET_ADDR ("127.0.0.1");         sockaddr.sin_port = htons (1234);         if (Connect (sock,  (sockaddr*) &sockaddr, sizeof (sockaddr))  == -1)          {             printf ("Failed conneCT (). \ n ");             wsacleanup ();             return 0;         }              // Gets the user-entered string and sends it to the server          char bufsend[buf_size] =  {0};        printf ("\ninput a string: ");         gets (bufsend);         int  i;        for (i=0; i<3; i++)          {            send ( Sock, bufsend, strlen (bufsend),  0);        }                 //data returned by the receiving server           Char bufrecv[buf_size] = {0};        int nrecv &NBSP;=&NBSP;RECV (sock, bufrecv, buf_size, 0);         if (nrecv > 0)         {             bufRecv[nRecv] =  ';       '       //Output received data              printf ("message from server: %s\n",  bufrecv);         }        memset (bufsend, 0, buf_size);// Reset buffer         memset (bufrecv, 0, buf_size);//Reset buffer                    //closing sockets          closesocket (sock);    }                      //termination of Use of dll     wsacleanup ();          return 0; }

Run server first, run client again, and enter the string "ABC" in 10 seconds, and wait a few seconds for the server to return data. The results of the operation are as follows:
Input a STRING:ABC
Message form SERVER:ABCABCABC

The key to this program is server.cpp line 31st code Sleep(10000); , which allows the program to suspend execution for 10 seconds. During this time, the client sends the string "ABC" three successive times, because the server is blocked, the data can only accumulate in the buffer, after 10 seconds, the server starts to run, reads out all the backlog data from the buffer once, and returns to the client.

It is also necessary to note that the 34th line of code is client.cpp. The client executes to the recv () function, because there is no data in the input buffer, it is blocked until the server returns data for 10 seconds before it begins execution. The visual effect that the user sees is that the client pauses for a period of time before outputting the results returned by the server.

The client's send () sends three packets, and the server's recv () receives only one packet, which is a good illustration of the sticky packet problem of the data.

The sticky packet problem of TCP and the non-boundary of data