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标题: TCP/IP网络编程第一例 [打印本页]

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作者: lutr    时间: 2008-5-1 10:48
标题: TCP/IP网络编程第一例
这几天一直在弄网络编程。今天终于弄出来了。与大家分享一下经验。
代码如下：
/*
* server.c-- Create a socket server
*/
#include
#include
#include
#include
#include

int port = 8001;

int main(void)
{
struct sockaddr_in sin;
struct sockaddr_in pin;
int sock_descriptor;
int temp_sock_descriptor;
int address_size;
char buf[16384];
int i, len;

sock_descriptor = socket(AF_INET, SOCK_STREAM, 0);
if(sock_descriptor == -1)
{
perror("call to socket");
exit(1);
}

bzero(&sin, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
sin.sin_port = htons(port);

if(bind(sock_descriptor, (struct sockaddr *)&sin, sizeof(sin)) == -1)
{
perror("call to bind");
exit(1);
}

if(listen(sock_descriptor,20) == -1)
{
perror("call to listen");
exit(1);
}
printf("Accepting connections ...\n");

while(1)
{
temp_sock_descriptor = accept(sock_descriptor, (struct sockaddr *)&pin, &address_size);
if(temp_sock_descriptor == -1)
{
perror("call to accept");
exit(1);
}

if(recv(temp_sock_descriptor, buf, 16384, 0) == -1)
{
perror("Call to recv");
exit(1);
}

printf("Now we starting recived the data ............................................\n");
printf("Recived from client: %s\n", buf);
//for this server example,we just convert the characters to upper case:

len = strlen(buf);
for(i = 0; i < len; i++)
buf = toupper(buf); //convert to input to capital

printf("Chevered recive data from client:%s\n", buf);

if(send(temp_sock_descriptor, buf, len, 0) == -1)
{
perror("call to send");
exit(1);
}
close(temp_sock_descriptor);
}
}

/*
* client.c -- the client of the TCP/IP
*/

#include
#include
#include
#include
#include

char *host_name = "127.0.0.1";
int port = 8001;

void main(int argc, char *argv[])
{
char buf[8192];
char message[256];

int socket_descriptor;
struct sockaddr_in pin;
struct hostent *server_host_name;

char *str = "A default test string";

if(argc < 2)
{
printf("Usage: 'test\" Any test string \"\n");
printf("We will send a default test string.\n");
}
else
str = argv[1];

if((server_host_name = gethostbyname(host_name)) == 0)
{
perror("Error resolving local host\n");
exit(1);
}

printf("Get host info is ok!\n");

bzero(&pin, sizeof(pin));
pin.sin_family = AF_INET;
pin.sin_addr.s_addr = htonl(INADDR_ANY);
pin.sin_addr.s_addr = ((struct in_addr *) (server_host_name->h_addr))->s_addr;

pin.sin_port = htons(port);

if((socket_descriptor = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
perror("Error opening socket\n");
exit(1);
}

if(connect(socket_descriptor, (void*)&pin, sizeof(pin)) == -1)
{
perror("Error connecting to socket\n");
exit(1);
}

printf("Sending message is : \n%s to server...\n", str);

if(send(socket_descriptor, str, strlen(str), 0) == -1)
{
perror("Error in send\n");
exit(1);
}

printf("...sent message... wait for response...\n");

if(recv(socket_descriptor, buf, 8192, 0) == -1)
{
perror("Error in receiving response from server\n");
exit(1);
}

printf("\nResponse from server:\n\n%s\n", buf);
close(socket_descriptor);
}
编写完这两个文件，然后再编写Make文件以便编译。Makefile文件如下：
client server: client.o server.o
gcc -o server server.o
gcc -o client client.o
client.o server.o: client.c server.c
gcc -c client.c
gcc -c server.c
clean:
rm -f client server *.o
使用make的目的是在修改代码后能够方便的编译。

完成上面的工作后，在命令行输入make回车即可进行编译，期间可能有些警告信息，不要理他。
你可以打开两个终端，以便于测试。先运行服务器程序等待客户端连接。然后再运行客户端程序。
运行结果如下：
服务器端结果
[hyj@localhost tcpip]$ ./server
Accepting connections ...
Now we starting recived the data ............................................
Recived from client: This is a test.
Chevered recive data from client:THIS IS A TEST.
使用ctrl＋C可以终止。
客户端结果
[hyj@localhost tcpip]$ ./client "This is a test."
Get host info is ok!
Sending message is :
This is a test. to server...
...sent message... wait for response...

Response from server:

THIS IS A TEST.
其中可能出现的错误有一下几点：
1.使用了已经被占用的端口；
2.指针错误的使用，尤其是在接收和发送这两个函数上；
3.套界字初始化有问题；
下面介绍其中的几个结构：
1.struct sockaddr{
unsigned short sa_family;//address family,FA_xxx
char sa_data[14];//14bytes of protocol address
}这个结构一般已经不再使用，常用sockaddr_in代替；
2.struct sockaddr_in{
short int sin_family;
unsigned short int sin_port;
struct in_addr sin_addr;
unsigned char sin_zero[8];//填充0以保持与sockaddr同样的大小
}
3.struct hostent{
char *h_name; //主机的正式名称
char **h_aliases; //别名列表
int h_addrtype;//主机地址类型：AF_xxx
int H_length;//主机地址长度：4字节
char **h_addr_list;//主机IP地址列表
}

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