一个很实用的服务端和客户端进行TCP通信的实例
本文给出一个很实用的服务端和客户端进行TCP通信的小例子。具体实现上非常简单，只是平时编写类似程序，具体步骤经常忘记，还要总是查，暂且将其记下来，方便以后参考。（1）客户端程序，编写一个文件client.c，内容如下：
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>/* netdb is necessary for struct hostent */
#define PORT 4321 /* server port */
#define MAXDATASIZE 100
int main(int argc, char *argv[])
{
int sockfd, num; /* files descriptors */
char buf; /* buf will store received text */
struct hostent *he; /* structure that will get information about remote host */
struct sockaddr_in server;
if (argc != 2)
{
printf("Usage: %s <IP Address>\n",argv);
exit(1);
}
if((he=gethostbyname(argv))==NULL)
{
printf("gethostbyname() error\n");
exit(1);
}
if((sockfd=socket(AF_INET,SOCK_STREAM, 0))==-1)
{
printf("socket() error\n");
exit(1);
}
bzero(&server,sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
server.sin_addr = *((struct in_addr *)he->h_addr);
if(connect(sockfd, (struct sockaddr *)&server, sizeof(server))==-1)
{
printf("connect() error\n");
exit(1);
}
char str[] = "horst\n"
if((num=send(sockfd,str,sizeof(str),0))==-1){
printf("send() error\n");
exit(1);
}
if((num=recv(sockfd,buf,MAXDATASIZE,0))==-1)
{
printf("recv() error\n");
exit(1);
}
buf='\0';
printf("server message: %s\n",buf);
close(sockfd);
return 0;
}（2）服务器端，编写server.c，内容如下
#include <sys/time.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define PORT 4321
#define BACKLOG 1
#define MAXRECVLEN 1024
int main(int argc, char *argv[])
{
char buf;
int listenfd, connectfd; /* socket descriptors */
struct sockaddr_in server; /* server's address information */
struct sockaddr_in client; /* client's address information */
socklen_t addrlen;
/* Create TCP socket */
if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
/* handle exception */
perror("socket() error. Failed to initiate a socket");
exit(1);
}
/* set socket option */
int opt = SO_REUSEADDR;
setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
bzero(&server, sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
server.sin_addr.s_addr = htonl(INADDR_ANY);
if(bind(listenfd, (struct sockaddr *)&server, sizeof(server)) == -1)
{
/* handle exception */
perror("Bind() error.");
exit(1);
}
if(listen(listenfd, BACKLOG) == -1)
{
perror("listen() error. \n");
exit(1);
}
addrlen = sizeof(client);
while(1){
if((connectfd=accept(listenfd,(struct sockaddr *)&client, &addrlen))==-1)
{
perror("accept() error. \n");
exit(1);
}
struct timeval tv;
gettimeofday(&tv, NULL);
printf("You got a connection from client's ip %s, port %d at time %ld.%ld\n",inet_ntoa(client.sin_addr),htons(client.sin_port), tv.tv_sec,tv.tv_usec);
int iret=-1;
while(1)
{
iret = recv(connectfd, buf, MAXRECVLEN, 0);
if(iret>0)
{
printf("%s\n", buf);
}else
{
close(connectfd);
break;
}
/* print client's ip and port */
send(connectfd, buf, iret, 0); /* send to the client welcome message */
}
}
close(listenfd); /* close listenfd */
return 0;
}
（3）编译运行以上两个程序放在同一个目录下，比如 /home/horstxu/Cprog/tcpCSmodel命令行进入该目录 $ cd /home/horstxu/Cprog/tcpCSmodel命令行执行 $ gcc -o client client.c ，可以编译出客户端程序。命令行执行 $ gcc -o server server.c，可以编译出服务端程序。命令行执行 $ ./server，启动server程序。这时你可能需要重新打开一个命令行窗口，到刚才的目录下，执行 $ ./client 127.0.0.1，启动客户端程序，就可以看到结果了。客户端：$ ./client 127.0.0.1
server message:horst
服务器端：$./server
you got a connection from client`s ip 127.0.0.1, port 60865 at time 1418281267.643428本程序客户端会自动退出，服务器不会，因此如果想停掉服务器程序，直接在命令行界面按键盘Ctrl+C停止。程序实现的功能很简单，就是服务器监听4321端口，客户端与之建立TCP连接后，再发送字符串“horst\n”到服务端，服务端打印出来，然后再把字符串传回给客户端，客户端再打印出来。然后客户端关闭连接退出，而服务端继续监听4321端口等待下一次连接。
服务端启动,客户端通过ip地址连接服务端,然后输入要发送的文件名,发送文件到服务段.
/*client.c*/
#include<netinet/in.h> // for sockaddr_in
#include<sys/types.h> // for socket
#include<sys/socket.h> // for socket
#include<stdio.h> // for printf
#include<stdlib.h> // for exit
#include<string.h> // for bzero
#define HELLO_WORLD_SERVER_PORT 6666
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
int main(int argc, char **argv)
{
if (argc != 2)
{
printf("Usage: ./%s ServerIPAddress\n", argv);
exit(1);
}
// 设置一个socket地址结构client_addr, 代表客户机的internet地址和端口
struct sockaddr_in client_addr;
bzero(&client_addr, sizeof(client_addr));
client_addr.sin_family = AF_INET; // internet协议族
client_addr.sin_addr.s_addr = htons(INADDR_ANY); // INADDR_ANY表示自动获取本机地址
client_addr.sin_port = htons(0); // auto allocated, 让系统自动分配一个空闲端口
// 创建用于internet的流协议(TCP)类型socket，用client_socket代表客户端socket
int client_socket = socket(AF_INET, SOCK_STREAM, 0);
if (client_socket < 0)
{
printf("Create Socket Failed!\n");
exit(1);
}
// 把客户端的socket和客户端的socket地址结构绑定
if (bind(client_socket, (struct sockaddr*)&client_addr, sizeof(client_addr)))
{
printf("Client Bind Port Failed!\n");
exit(1);
}
// 设置一个socket地址结构server_addr,代表服务器的internet地址和端口
struct sockaddr_inserver_addr;
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
// 服务器的IP地址来自程序的参数
if (inet_aton(argv, &server_addr.sin_addr) == 0)
{
printf("Server IP Address Error!\n");
exit(1);
}
server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);
socklen_t server_addr_length = sizeof(server_addr);
// 向服务器发起连接请求，连接成功后client_socket代表客户端和服务器端的一个socket连接
if (connect(client_socket, (struct sockaddr*)&server_addr, server_addr_length) < 0)
{
printf("Can Not Connect To %s!\n", argv);
exit(1);
}
char file_name;
bzero(file_name, sizeof(file_name));
printf("Please Input File Name On Server.\t");
scanf("%s", file_name);
char buffer;
bzero(buffer, sizeof(buffer));
strncpy(buffer, file_name, strlen(file_name) > BUFFER_SIZE ? BUFFER_SIZE : strlen(file_name));
// 向服务器发送buffer中的数据，此时buffer中存放的是客户端需要接收的文件的名字
send(client_socket, buffer, BUFFER_SIZE, 0);
FILE *fp = fopen(file_name, "w");
if (fp == NULL)
{
printf("File:\t%s Can Not Open To Write!\n", file_name);
exit(1);
}
// 从服务器端接收数据到buffer中
bzero(buffer, sizeof(buffer));
int length = 0;
while(length = recv(client_socket, buffer, BUFFER_SIZE, 0))
{
if (length < 0)
{
printf("Recieve Data From Server %s Failed!\n", argv);
break;
}
int write_length = fwrite(buffer, sizeof(char), length, fp);
if (write_length < length)
{
printf("File:\t%s Write Failed!\n", file_name);
break;
}
bzero(buffer, BUFFER_SIZE);
}
printf("Recieve File:\t %s From Server[%s] Finished!\n", file_name, argv);
// 传输完毕，关闭socket
fclose(fp);
close(client_socket);
return 0;
}
/*server.c*/
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define HELLO_WORLD_SERVER_PORT 6666 //端口号
#define LENGTH_OF_LISTEN_QUEUE 20
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
int main(int argc, char **argv)
{
// set socket's address information
// 设置一个socket地址结构server_addr,代表服务器internet的地址和端口
struct sockaddr_in server_addr;
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htons(INADDR_ANY);
server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);
// create a stream socket
// 创建用于internet的流协议(TCP)socket，用server_socket代表服务器向客户端提供服务的接口
int server_socket = socket(PF_INET, SOCK_STREAM, 0);
if (server_socket < 0)
{
printf("Create Socket Failed!\n");
exit(1);
}
// 把socket和socket地址结构绑定
if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)))
{
printf("Server Bind Port: %d Failed!\n", HELLO_WORLD_SERVER_PORT);
exit(1);
}
// server_socket用于监听
if (listen(server_socket, LENGTH_OF_LISTEN_QUEUE))
{
printf("Server Listen Failed!\n");
exit(1);
}
// 服务器端一直运行用以持续为客户端提供服务
while(1)
{
// 定义客户端的socket地址结构client_addr，当收到来自客户端的请求后，调用accept
// 接受此请求，同时将client端的地址和端口等信息写入client_addr中
struct sockaddr_in client_addr;
socklen_t length = sizeof(client_addr);
// 接受一个从client端到达server端的连接请求,将客户端的信息保存在client_addr中
// 如果没有连接请求，则一直等待直到有连接请求为止，这是accept函数的特性，可以
// 用select()来实现超时检测
// accpet返回一个新的socket,这个socket用来与此次连接到server的client进行通信
// 这里的new_server_socket代表了这个通信通道
int new_server_socket = accept(server_socket, (struct sockaddr*)&client_addr, &length);
if (new_server_socket < 0)
{
printf("Server Accept Failed!\n");
break;
}
char buffer;
bzero(buffer, sizeof(buffer));
length = recv(new_server_socket, buffer, BUFFER_SIZE, 0);
if (length < 0)
{
printf("Server Recieve Data Failed!\n");
break;
}
char file_name;
bzero(file_name, sizeof(file_name));
strncpy(file_name, buffer,
strlen(buffer) > FILE_NAME_MAX_SIZE ? FILE_NAME_MAX_SIZE : strlen(buffer));
FILE *fp = fopen(file_name, "r");
if (fp == NULL)
{
printf("File:\t%s Not Found!\n", file_name);
}
else
{
bzero(buffer, BUFFER_SIZE);
int file_block_length = 0;
while( (file_block_length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)
{
printf("file_block_length = %d\n", file_block_length);
// 发送buffer中的字符串到new_server_socket,实际上就是发送给客户端
if (send(new_server_socket, buffer, file_block_length, 0) < 0)
{
printf("Send File:\t%s Failed!\n", file_name);
break;
}
bzero(buffer, sizeof(buffer));
}
fclose(fp);
printf("File:\t%s Transfer Finished!\n", file_name);
}
close(new_server_socket);
}
close(server_socket);
return 0;
}
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