Linux_C socket clinet.c

 1 /* timeclnt.c - a client for timeserv.c
 2  *              usage: timeclnt hostname portnumber
 3  */
 4 #include <stdio.h>
 5 #include <sys/types.h>
 6 #include <sys/socket.h>
 7 #include <netinet/in.h>
 8 #include <netdb.h>
 9 
10 #define oops(msg) {perror(msg); exit(1); }
11 #define oopsn(msg, x) {perror(msg); exit(x);};
12 int main(int argc, char* argv[]) {
13   struct sockaddr_in servadd; 
14   struct hostent *hp;
15   int sock_id, sock_fd;
16   char message[BUFSIZ];
17   int messlen;
18   int connect_num;
19   /*** Step 1: Get a socket ***/
20   sock_id=socket(PF_INET, SOCK_STREAM, 0);
21   if(sock_id==-1)
22     oops("socket");
23   /*** Step 2: connect to server need to build address (host, port)of server first ***/
24   bzero((void*)&servadd, sizeof(servadd));
25   hp=gethostbyname(argv[1]);
26   if(hp==NULL)
27     oops(argv[1]);
28 
29   bcopy(hp->h_addr, (struct sockaddr*)&servadd.sin_addr, hp->h_length);
30   servadd.sin_port=htons(atoi(argv[2]));/**这里记住一定要atoi转换，不然connect不起**/
31   servadd.sin_family=AF_INET;
32 
33   if((connect_num=connect(sock_id, (struct sockaddr*)&servadd, sizeof(servadd)))!=0)
34     {  
35       printf("connect fail is %d.",connect_num);
36       oopsn("connnnnect!!!!!", connect_num);
37     }
38   
39   /*** Step 3: transfer data from server , then hangup ***/
40   messlen=read(sock_id, message, BUFSIZ);
41   if(messlen == 1)
42     oops("read");
43   if(write(1, message, messlen)!= messlen)
44     oops("write");
45   close(sock_id);
46   return 0;
47 }