通過本文你會了解到:
1. TCP server的實例
2. TCP client的實例
3. TCP server和client的運行測試
4. TCP C/S模型的思考
約定
1. 格式爲 /**/ 的註釋對程序的主要流程進行說明
2. 格式爲 // 的註釋對程序的難懂語句進行說明
TCP server實例(server.c)
#include <stdio.h> /* for printf() and fprintf() */
#include <sys/types.h> /* for Socket data types */
#include <sys/socket.h> /* for socket(), connect(), send(), and recv() */
#include <netinet/in.h> /* for IP Socket data types */
#include <arpa/inet.h> /* for sockaddr_in and inet_addr() */
#include <stdlib.h> /* for exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
#include <errno.h> /* for errno*/
//macro
#define BUF_SIZE 1024
#define PORT 1025
#undef max
#define max(x, y) ((x) > (y) ? (x) : (y))
#undef handle_error
#define handle_error(msg) \
do { perror(msg); exit(EXIT_FAILURE); } while(0)
int main(int argc, char *argv[])
{
struct sockaddr_in server_addr;
struct sockaddr_in conn_addr;
fd_set read_fds;
socklen_t len;
char buf[BUF_SIZE];
int conn_fd = -1;
int server_fd = -1;
int ret;
/*創建tcp描述符*/
server_fd = socket(AF_INET, SOCK_STREAM, 0);
if(server_fd == -1)
handle_error("socket");
/*指定server信息並綁定*/
memset(&server_addr, 0, sizeof(struct sockaddr_in));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(PORT);
server_addr.sin_addr.s_addr = htonl(INADDR_ANY); //ip地址爲任意,只要port滿足即可
if(bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1)
handle_error("bind");
/*監聽server描述符*/
if(listen(server_fd, 5) == -1)
handle_error("listen");
printf("accepting connections on port %d\n", PORT);
while(1) {
int max_fd = 0;
FD_ZERO(&read_fds);
FD_SET(server_fd ,&read_fds);
max_fd = max(server_fd, max_fd);
if(conn_fd > 0) {
FD_SET(conn_fd ,&read_fds);
max_fd = max(conn_fd, max_fd);
}
/*檢測描述符集中的描述符的I/O狀態*/
ret = select(max_fd + 1, &read_fds, NULL, NULL, NULL);
if(ret == -1 && errno == EINTR)
continue;
if(ret == -1)
handle_error("select");
if(FD_ISSET(server_fd, &read_fds)) { //server_fd可讀,即有client連接
len = sizeof(conn_addr);
if(conn_fd > 0) { //如果已有連接,則先關閉,因此此server只與最後一次連接的client進行通信
close(conn_fd);
}
/*接受並得到client信息*/
conn_fd = accept(server_fd, (struct sockaddr *)&conn_addr, &len);
if(conn_fd == -1)
handle_error("accept");
printf("client is connected\n");
} else if(FD_ISSET(conn_fd, &read_fds)) { //conn_fd可讀,即接收到client數據
int n;
memset(buf, 0, BUF_SIZE);
n = recv(conn_fd, buf, BUF_SIZE, 0);
if(n == -1) { //recv函數返回錯誤
perror("recv");
close(conn_fd);
conn_fd = -1;
} else if(n == 0) { //client端套接字被關閉
printf("client is closed\n");
close(conn_fd);
conn_fd = -1;
} else { //讀取成功
/*對收到的數據進行處理*/
printf("receive data:%s\n", buf);
}
}
}
/*關閉描述符*/
close(server_fd);
return 0;
}
TCP client實例(client.c)
#include <stdio.h> /* for printf() */
#include <sys/types.h> /* for Socket data types */
#include <sys/socket.h> /* for socket(), connect(), send(), and recv() */
#include <netinet/in.h> /* for IP Socket data types */
#include <arpa/inet.h> /* for sockaddr_in and inet_addr() */
#include <stdlib.h> /* for exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
#include <errno.h> /* for errno*/
//macro
#define BUF_SIZE 1024
#define PORT 1025
#define SEND_PACK_CNT 3
#define SRV_IP "127.0.0.1"
#undef handle_error
#define handle_error(msg) \
do { perror(msg); exit(EXIT_FAILURE); } while(0)
int main(int argc, char *argv[])
{
struct sockaddr_in server_addr;
char buf[BUF_SIZE];
int conn_fd = -1;
int i;
/*創建tcp描述符*/
conn_fd = socket(AF_INET, SOCK_STREAM, 0);
if(conn_fd == -1)
handle_error("socket");
/*指定將連接的server信息*/
memset(&server_addr, 0, sizeof(struct sockaddr_in));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(PORT);
if (inet_aton(SRV_IP, &server_addr.sin_addr) == 0)
handle_error("inet_aton");
/*連接到server*/
if(connect(conn_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1)
handle_error("connect");
printf("connect to server ip:%s port:%d\n", SRV_IP, PORT);
for(i = 0; i < SEND_PACK_CNT; i++) {
sprintf(buf, "Packet %d", i);
printf("send to server: %s\n", buf);
/*發送數據*/
send(conn_fd, buf, strlen(buf) + 1, 0);
sleep(2);
}
/*關閉描述符*/
printf("close\n");
close(conn_fd);
return 0;
}
TCP server和client的運行測試
TCP C/S模型的思考
在TCP連接關閉時,連接會進入TIME_WAIT狀態,經過2個MSL時間後關閉,因此如果client頻繁連接和關閉,如果在2個MSL時間內令連接數達到1024則下一次將會返回失敗。