Reputation: 11
I have a little problem with sending and receiving a string with socket between a server and a client. In this code, first the server sends "connection established ("connessione avvenuta" in Italian) to the client (which prints it on screen), then the client scans a string and sends it to the server, which deletes the vowels and sends it again to the client. When I print it with client, strange chars appears at the end of the string, I think because I didn't close it well. How to do this?
**SERVER SIDE**
#if defined WIN32
#include <winsock2.h>
#else
#define closesocket close
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFSIZE 30
void ClearWinSock() {
#if defined WIN32
WSACleanup();
#endif
}
int main(void) {
//---------------------------INIZIALIZZAZIONE WSADATA
#if defined WIN32
WSADATA wsaData;
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf ("Error at WSAStartup");
return 0;
}
#endif
//-------------------------------CREAZIONE SOCKET
int Mysocket;
Mysocket = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
if (Mysocket < 0) {
printf("socket creation failed\n");
return 0;
}
struct sockaddr_in sad;
memset(&sad, 0, sizeof(sad));
sad.sin_family = AF_INET;
sad.sin_addr.s_addr = inet_addr ("127.0.0.1");
sad.sin_port = htons (9888);
//------------------------ASSEGNAZIONE PORTA E IP ALLA SOCKET
if (bind(Mysocket, (struct sockaddr*) &sad, sizeof(sad)) <0) {
printf ("bind() failed\n");
closesocket(Mysocket);
return 0;
}
//---------------------------SETTAGGIO SOCKET ALL'ASCOLTO
int qlen = 10;
if (listen (Mysocket, qlen) < 0) {
printf("listen() failed\n");
closesocket(Mysocket);
return 0;
}
struct sockaddr_in cad;
int Csocket;
int clientlen;
//------------------------------ACCETTA LA CONNESSIONE
while (1) {
printf("In attesa di un client con cui comunicare\n");
memset(&cad, 0, sizeof(cad));
clientlen = sizeof(cad);
if((Csocket = accept(Mysocket, (struct sockaddr*) &cad, &clientlen)) < 0) {
printf ("accept failed\n");
closesocket(Mysocket);
ClearWinSock();
return 0;
}
printf("connesso con il client\n");
//---------------------------------------INVIO STRINGA AL CLIENT
char* inputString = "connessione avvenuta";
int stringlen = strlen(inputString);
if (send(Csocket, inputString, stringlen, 0) != stringlen) {
printf("client-send() sent a different number of bytes than expected");
closesocket(Csocket);
ClearWinSock();
system ("pause");
return 0;
}
//-------------------------------------RICEZIONE STRINGA DAL CLIENT
char str1[BUFSIZE+1]; char str1des[BUFSIZE+1];
int i,j=0;
//recv (Csocket, str1, BUFSIZE - 1, 0);
int read = recv(Csocket, str1, BUFSIZE-1, 0); str1[read] = '\0';
//-------------------------------ELIMINAZIONE VOCALI DALLA STRINGA RICEVUTA
for(i=0;i<=strlen(str1)+1;i++) {
if(str1[i]=='a'||str1[i]=='e'||str1[i]=='i'||str1[i]=='o'||str1[i]=='u' ||str1[i]=='A'||str1[i]=='E'||str1[i]=='I'||str1[i]=='O'||str1[i]=='U')
str1[i]=' ';
else
str1des[j++]=str1[i];
}
str1des[j]='\0';
//-----------------------------------INVIO STRINGA ELABORATA AL CLIENT
if (send(Csocket, str1des, strlen(str1des), 0) != strlen(str1des)) {
printf("client-send() sent a different number of bytes than expected");
closesocket(Csocket);
ClearWinSock();
system ("pause");
return 0;
}
}
//------------------------------------------CHIUSURA CONNESSIONE
closesocket (Csocket);
ClearWinSock();
printf ("\n");
system ("pause");
return 0;
}
**CLIENT SIDE**
#if defined WIN32
#include <winsock2.h>
#else
#define closesocket close
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFSIZE 30
void ClearWinSock() {
#if defined WIN32
WSACleanup();
#endif
}
//-----------------------------INIZIALIZZAZIONE WSADATA
int main (void) {
#if defined WIN32
WSADATA wsaData;
int iResult = WSAStartup (MAKEWORD (2,2), &wsaData);
if (iResult !=0) {
printf ("error at WSASturtup\n");
return 0;
}
#endif
//--------------------------------CREAZIONE SOCKET
int Csocket;
Csocket = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP);
if (Csocket < 0) {
printf ("socket creation failed");
closesocket (Csocket);
ClearWinSock();
return 0;
}
//--------------------------COSTRUZIONE INDIRIZZO SERVER
struct sockaddr_in sad;
memset (&sad, 0, sizeof(sad));
sad.sin_family = AF_INET;
sad.sin_addr.s_addr = inet_addr ("127.0.0.1");
sad.sin_port = htons (9888);
//------------------------------CONNESSIONE AL SERVER
if (connect(Csocket, (struct sockaddr*) &sad, sizeof(sad)) < 0) {
printf ("failed to connect\n");
closesocket (Csocket);
ClearWinSock();
return 0;
}
//-----------------------------RICEZIONE DATI DAL SERVER
char buf[BUFSIZE+1];
int read = recv (Csocket, buf, BUFSIZE - 1, 0);
if (read <=0) {
printf ("Qualcosa non và!\n");
}
else {
buf[read+1] = '\0';
printf("Server scrive: %s\n", buf);
}
//----------------------------INVIO PRIMA STRINGA AL SERVER
char str1[BUFSIZE+1]; int stringlen = strlen(str1);
printf ("inserisci prima stringa:\n");
scanf ("%s", str1);
if (send(Csocket, str1, stringlen, 0) != stringlen) {
printf("client-send() sent a different number of bytes than expected");
closesocket(Csocket);
ClearWinSock();
system ("pause");
return 0;
}
//------------------------------RICEZIONE STRINGA ELABORATA DAL SERVER
char buf2[BUFSIZE+1];
int read2 = recv (Csocket, buf2, BUFSIZE - 1, 0);
if (read2 <=0) {
printf ("Qualcosa non và!\n");
}
else {
buf2[read+1] = 0;
printf("Server scrive: %s\n", buf2);
}
//---------------------------------------CHIUSURA CONNESSIONE
closesocket (Csocket);
ClearWinSock();
printf ("\n");
system ("pause");
return 0;
}
Upvotes: 0
Views: 160
Reputation: 185
With TCP protocol, send() and recv() doesn't necessary write/read the length given in parameters. You need to check the return value to know how much bytes has been write/read on the socket.
There are 2 simple methods to send/read string on sockets:
Use a header.
In the packet you write on the socket, you include the string size just before the string.
Example, if you write "hello", the packet you'll send will be formed like this:
+---------+---------------+
| uint8_t | char[size] |
+--------------------------+
| 0x5 | "hello" |
+---------+---------------+
With this method, when you read on the socket, you first read the header ( 1 byte in the example ) then you read N bytes to get the complete string.
Don't forget to add the '\0' at the end of the string.
Include the '/0' at the end of the string.
+------------------+
| char[size + 1] |
+------------------+
| "hello\0" |
+------------------+
By this way, you read on the socket until you get a '\0'
Upvotes: 1