Linux Socket 编程实例(一个Hello World程序)

在Linux下写了个小的socket程序，分为客户端和服务器端,服务端开一个端口(2000),做为一个daemon,等待客户的连接请求.一旦有客 户连接,服务器端打印出客户端的IP地址和端口,并且向服务器端发送欢迎信息和时间.下面是服务端的代码(tcpserver.c).由于这只是个简单的 程序，所以只用了单线程实现!

[代码] tcpserver.c

01    /**
02     * Tcp Server program, It is a simple example only.
03     * zhengsh 200520602061 2
04     * when client connect to server, send a welcome message and timestamp in server.
05     */
06
07    #include  <stdio.h>
08    #include  <sys/socket.h>
09    #include  <unistd.h>
10    #include  <sys/types.h>
11    #include  <netinet/in.h>
12    #include  <stdlib.h>
13    #include  <time.h>
14
15    #define  SERVER_PORT 20000  //  define the defualt connect port id
16    #define  LENGTH_OF_LISTEN_QUEUE 10  // length of listen queue in server
17    #define  BUFFER_SIZE 255
18    #define  WELCOME_MESSAGE "welcome to connect the server. "
19
20    int main(int argc, char** argv)
21    {
22           int  servfd,clifd;
23           struct  sockaddr_in servaddr,cliaddr;
24
25           if  ((servfd  =  socket(AF_INET,SOCK_STREAM, 0 ))  <   0 )
26             {
27                  printf( " create socket error!\n " );
28                  exit( 1 );
29           }
30
31           bzero( & servaddr, sizeof (servaddr));
32
33           servaddr.sin_family  =  AF_INET;
34           servaddr.sin_port  =  htons(SERVER_PORT);
35           servaddr.sin_addr.s_addr  =  htons(INADDR_ANY);
36
37           if  (bind(servfd,( struct  sockaddr * ) & servaddr, sizeof (servaddr)) < 0 )
38             {
39                  printf( " bind to port %d failure!\n " ,SERVER_PORT);
40                  exit( 1 );
41           }
42
43            if  (listen(servfd,LENGTH_OF_LISTEN_QUEUE)  <   0 )
44             {
45                  printf( " call listen failure!\n " );
46                  exit( 1 );
47           }
48
49            while  ( 1 )
50             { // server loop will nerver exit unless any body kill the process
51
52                  char  buf[BUFFER_SIZE];
53                  long  timestamp;
54                  socklen_t length  =   sizeof (cliaddr);
55                  clifd  =  accept(servfd,( struct  sockaddr * ) & cliaddr, & length);
56
57                   if  (clifd  <   0 )
58                    {
59                         printf( " error comes when call accept!\n " );
60                         break ;
61                  }
62
63                  strcpy(buf,WELCOME_MESSAGE);
64
65                   // inet_ntop(INET_ADDRSTRLEN,cliaddr.sin_addr,buf,BUFFER_SIZE);
66
67                  printf( " from client,IP:%s,Port:%d\n " ,
68                     inet_ntoa(cliaddr.sin_addr),ntohs(cliaddr.sin_port));
69
70                  timestamp  =  time(NULL);
71
72                  strcat(buf, " timestamp in server: " );
73                  strcat(buf,ctime( & timestamp));
74
75                  send(clifd,buf,BUFFER_SIZE, 0 );
76
77                  close(clifd);
78
79           } // exit
80
81           close(servfd);
82
83           return   0 ;
84    }

[代码] tcpclient.c

01    /**
02     * Tcp client program, It is a simple example only.
03     * zhengsh 200520602061 2
04     * connect to server, and echo a message from server.
05     */
06
07
08    #include <stdio.h>
09    #include <sys/socket.h>
10    #include <unistd.h>
11    #include <sys/types.h>
12    #include <netinet/in.h>
13    #include <stdlib.h>
14
15
16    #define  SERVER_PORT 20000  //  define the defualt connect port id
17    #define  CLIENT_PORT ((20001+rand())%65536)  //  define the defualt client port as a random port
18    #define  BUFFER_SIZE 255
19    #define  REUQEST_MESSAGE "welcome to connect the server.\n"
20
21
22    void  usage(char* name)
23    {
24           printf( " usage: %s IpAddr\n " ,name);
25    }
26
27
28    int  main(int argc, char** argv)
29    {
30           int  servfd,clifd,length = 0;
31           struct  sockaddr_in servaddr,cliaddr;
32           socklen_t socklen  =   sizeof (servaddr);
33           char  buf[BUFFER_SIZE];
34
35            if (argc < 2 )
36             {
37                  usage(argv[ 0 ]);
38                  exit( 1 );
39           }
40
41           if ((clifd  =  socket(AF_INET,SOCK_STREAM, 0 ))  <   0 )
42             {
43                 printf( " create socket error!\n " );
44                 exit( 1 );
45           }
46
47           srand(time(NULL)); // initialize random generator
48
49           bzero( & cliaddr, sizeof (cliaddr));
50           cliaddr.sin_family  =  AF_INET;
51           cliaddr.sin_port  =  htons(CLIENT_PORT);
52           cliaddr.sin_addr.s_addr  =  htons(INADDR_ANY);
53
54           bzero( & servaddr, sizeof (servaddr));
55           servaddr.sin_family  =  AF_INET;
56           inet_aton(argv[ 1 ], & servaddr.sin_addr);
57           servaddr.sin_port  =  htons(SERVER_PORT);
58          // servaddr.sin_addr.s_addr = htons(INADDR_ANY);
59
60           if  (bind(clifd, (struct sockaddr* ) &cliaddr, sizeof (cliaddr)) < 0 )
61           {
62                  printf( " bind to port %d failure!\n " ,CLIENT_PORT);
63                  exit( 1 );
64           }
65
66            if (connect(clifd,( struct  sockaddr * ) & servaddr, socklen)  <   0 )
67           {
68                  printf( " can't connect to %s!\n ", argv[ 1 ]);
69                  exit( 1 );
70           }
71
72           length  =  recv(clifd, buf, BUFFER_SIZE, 0);
73            if  (length < 0)
74            {
75                  printf( " error comes when recieve data from server %s! ", argv[1] );
76                  exit( 1 );
77           }
78
79           printf( " from server %s :\n\t%s", argv[1], buf);
80
81           close(clifd);
82           return 0;
83    }