CODEWITHSUNDEEP
csockets
user61652
user61652

Reputation: 93

how read all the server's responses from a socket?

I have a very big problem... I'm working with sockets in C. I send a request to the server which sends me many responses. The problem is that the client receives the first response and then the connection is closed. What can I do? I tried with setsockopt()... SO_KEEPALIVE or SO_LINGER but I haven't resolved the problem. Can you help me? Thanks a lot

To be more clear here is the code. The socket is automatically closed after a certain amount of time or after the client received the first response... I'm not sure.

char* demarre_client( client_args * c_args,char* message, /*char* SERVEUR_PORT*/int port){
int socket_client=socket(PF_INET,SOCK_STREAM,0);
memset(&(c_args->adresse_serveur),0,sizeof(c_args->adresse_serveur));
c_args->adresse_serveur.sin_family=AF_INET;
c_args->adresse_serveur.sin_addr.s_addr=inet_addr(SERVEUR_IP);
//int port=APHash(SERVEUR_PORT,strlen(SERVEUR_PORT));
c_args->adresse_serveur.sin_port=htons(port);
int err=0;

if ((err=connect(socket_client, (struct sockaddr *) &(c_args->adresse_serveur), sizeof(c_args->adresse_serveur)))<0)
{
    printf("CONNECT error %d\n", errno);
    exit(-1);
}
if (send(socket_client, message, strlen(message), 0)!=strlen(message))
{
    printf("send error!!\n");
    exit(-2);
}
char* raspFin=(char* )malloc(sizeof(char)*1024);
strcpy(raspFin,"");
int num=-1;
int nn=0;
char* rasp=(char* )malloc(sizeof(char)*1024);
memset (rasp, 0, 1024 * sizeof(char ));
    /* here it reads the first response and after he get out of while */
while ((num=recv(socket_client, rasp,1024,MSG_WAITALL))>0)
{
    printf("recu %s mun=%d\n" , rasp,num);
    strcat(raspFin,rasp);
    strcat(raspFin,"\n");
    rasp=(char* )malloc(sizeof(char)*1024);
    memset (rasp, 0, 1024 * sizeof(char ));

}

if (num<0)
{
    printf("rasp error!!\n");
    exit(-3);
}

Upvotes: 1

Views: 1205

Answers (2)

Saulius Žemaitaitis
Saulius Žemaitaitis

Reputation: 2974

My suggestion would be to fire up Wireshark network analyzer and see what's happening packet-wise. In filters set 

tcp.srcport == <insert_server_port> || tcp.dstport == <insert_server_port>

You should see what data actually gets sent to and who closes the connection (sends FIN/RST packets).

Upvotes: 2

qrdl
qrdl

Reputation: 34968

Are you sure you don't get all responses on first call?

TCP/IP is stream protocol without flow control built-in so different messages, sent using separate send() calls, can be received in one recv(). Because you use printf(), it prints the buffer until it sees null-terminator - maybe other responses beyond the terminator?

Try to use some flow control, like sending message length prefix or using some special characters (like STX/ETX, but make sure your message doesn't contain such characters). You'd need to implement some flow-control anyway if you plan to use this software.

For now try replacing your printf() with

char *ptr;
for (ptr = buffer; ptr <= buffer + num; ptr += strlen(ptr)+1;)
    printf("%s\n", ptr);

It will print all strings from your response buffer.

And you don't need malloc() inside the loop - you leak memory.

BTW SO_KEEPALIVE and SO_LINGER have nothing to do with this problem.

Upvotes: 4

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