C sockets programming questions

[methodtwo]

Hi there
I'm trying to write a client and server as an exercise in learning the sockets api. The client needs to send the server 2 integers to provide X,Y coordinates for a "move" in a game of tic-tac-toe. The server just verifies that the coordinates are in range. If they're not a text string is sent back. If they are then the two coordinates are sent back to the client. If i have:

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void get_player_move(void)
{

 int len;
 int n=0;

 char sendline[16], recvline[30]; 
 
   int x, y;
   printf("Enter X,Y coordinates for your move: ");
   scanf( "%d%d", &x, &y);
   snprintf(sendline, sizeof(sendline), "%c%c\n", x, y);

   for(;;) {
     if(n > 0) {
       printf("Enter X,Y coordinates for your move: ");
       scanf("%d%d", &x, &y);
       snprintf(sendline, sizeof(sendline), "%c%c\n", x, y);
     }
     if(sendto(sockfd, sendline, sizeof(sendline), 0, res->ai_addr, res->ai_addrlen) ==-1){
	   perror("sendto failed");
	   exit(1);
  }
     if(recvfrom(sockfd, recvline, sizeof(recvline), 0, res->ai_addr, &res->ai_addrlen) ==-1){
       perror("recvfrom failed");
       exit(1);
   }
   if(sscanf(recvline, "%d%d", &x, &y) == 2)
     break;
   else
     printf("%s\n", recvline);
     n++;   
  }
  matrix[x][y] = 'X';
}

for the client. And

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void get_player_move(void)
{
   char recvline[16], sendline[30], textline[30];
   int x, y; 

   for(;;){
   if(recvfrom(sockfd, recvline, sizeof(recvline), 0,(struct sockaddr*)&cli_addr, &cli_len) ==-1){
     perror("recvfrom error");
     exit(1);
   }

   if(sscanf(recvline, "%d%d", &x, &y) != 2){
      perror("sscanf error on server");
      exit(1);
   }
   x--; y--;
   printf("x is %d, y is %d\n", x, y);
   if(matrix[x][y] != ' '){
    snprintf(textline, sizeof(textline), "Invalid move, try again.\n");
    if(sendto(sockfd, textline, sizeof(textline), 0, (struct sockaddr*)&cli_addr,cli_len)  ==-1){
       perror("sendto failed");
       exit(1);
   }
    
   }
   else {
        matrix[x][y] = 'X';
        snprintf(sendline, sizeof(sendline), "%c%c\n", x, y);
   if(sendto(sockfd, sendline, sizeof(sendline), 0, (struct sockaddr*)&cli_addr, cli_len) ==-1){
     perror("send move back failed");
     exit(1);
    }
   else
       /*break;*/
       exit(0);
  }
 }
}

Then why does the call to sscanf fail on the server? I thought that snprintf and sscanf could format between data types(?). Could someone let me know what is wrong with this code as far as datatypes and conversion is concerned? I don't need help with the "protocol". I think blocking in recvfrom and "iterative" is fine for a udp exercise.
Thank you very much for any help

[syn0ptik]

Better do comparsion with non zero.

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if(sscanf(recvline, "%d%d", &x, &y) != 0)

[methodtwo]

Thank you very much for the reply. I didn't understand it though. I mean:

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if(sscanf(recvline, "%d%d", &x, &y) != 0)

Means "if there was no failure" whereas the code i had before meant "if the values were assigned correctly" What is the benfit of doing it the "!= 0" way?. It's just the same but with the logic inverted isn't it?

[floppymaster]

You are trying to parse two integers with nothing in between them. How is sscanf supposed to know where the first number stops and the second one starts?

[methodtwo]

Thank you very much for the reply. Got it all working thanks to you. valhallas of data-flow from sweet gentoo!