TCP协议是一种面向连接的、可靠的、基于字节流的传输层通信协议。通讯过程如下:
服务器端先初始化Socket,然后与端口绑定(bind),对端口进行监听(listen),调用accept阻塞,等待客户端连接。在这时如果有个客户端初始化一个Socket,然后连接服务器(connect),如果连接成功,这时客户端与服务器端的连接就建立了。客户端发送数据请求,服务器端接收请求并处理请求,然后把回应数据发送给客户端,客户端读取数据,最后关闭连接,一次交互结束。
服务端代码:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/ipc.h>
#include <errno.h>
#include <sys/shm.h>
#include <time.h>
#include <pthread.h>
#include <arpa/inet.h>
#define BUFFER_SIZE 1024 // buf size
#define LISTENQ 1 // the max quote
#define SIZE_SHMADD 2048
int main(int argc, char *argv[]) {
// check the arguments.
if (argc != 2) {
printf("Usage:\n");
printf(" %s <port number>\n", argv[0]);
return -1;
}
struct sockaddr_in server_addr;
struct sockaddr_in client_addr;
char recv_buf[BUFFER_SIZE];
char send_buf[BUFFER_SIZE];
pid_t pid;
int sock_fd, conn_fd = -1;
int optval = 1;
int port = atoi(argv[1]);
if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
perror("socket");
return -1;
}
// setting bind port crycled.
if ((setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR,
(void *)&optval, sizeof(int))) < 0) {
perror("setsockopt");
goto err;
}
// initized address.
bzero(&server_addr, sizeof(struct sockaddr_in));
server_addr.sin_family=AF_INET;
server_addr.sin_addr.s_addr=htonl(INADDR_ANY);
server_addr.sin_port = htons(port);
// bind the port.
if (bind(sock_fd, (struct sockaddr *)(&server_addr),
sizeof(struct sockaddr)) == -1) {
perror("bind");
goto err;
}
// transform the socket into listen socket.
if (listen(sock_fd, LISTENQ) == -1) {
perror("listen");
goto err;
}
printf("Waiting for client connectionn...\n");
socklen_t cli_len = sizeof(struct sockaddr_in);
conn_fd = accept(sock_fd, (struct sockaddr *)(&client_addr), &cli_len);
if (conn_fd == -1) {
perror("accept");
close(sock_fd);
return -1;
}
printf("Client accepted : %s:%d \n",
inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
pid = fork();
if (pid > 0) {
// The parent process is responsible for sending messages.
while (1) {
bzero(send_buf, sizeof(send_buf));
char *str = fgets(send_buf, sizeof(send_buf), stdin);
if (str == NULL) {
perror("fgets");
goto err;
}
if (send(conn_fd, send_buf, strlen(send_buf) - 1, 0) < 0) {
perror("send");
goto err;
}
}
}
else if (pid == 0) {
// The child process is responsible for receiving messages.
while (1) {
bzero(recv_buf, sizeof(recv_buf));
if ((recv(conn_fd, recv_buf, BUFFER_SIZE, 0)) <= 0) {
perror("recv");
goto err;
}
printf("[Recv from client %s:%d] : %s\n",
inet_ntoa(server_addr.sin_addr),
htons(server_addr.sin_port),
recv_buf);
}
}
else {
perror("fork");
goto err;
}
close(conn_fd);
close(sock_fd);
return 0;
err:
close(conn_fd);
close(sock_fd);
return -1;
}
客户端代码:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define BUFFER_SIZE 1024
int main(int argc, char *argv[]) {
// check the arguments.
if (argc != 3) {
printf("Usage:\n");
printf(" %s <server addr> <port number>\n", argv[0]);
return -1;
}
char *addr = argv[1];
short port = atoi(argv[2]);
int sock_fd;
int ret;
char recv_buf[BUFFER_SIZE], send_buf[BUFFER_SIZE];
struct sockaddr_in server_addr;
// initialize address/
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(port);
server_addr.sin_addr.s_addr = inet_addr(addr);
// create socket fd.
sock_fd = socket(AF_INET, SOCK_STREAM, 0);
if (sock_fd == -1) {
perror("socket");
return -1;
}
// connect.
ret = connect(sock_fd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr));
if (ret == -1) {
perror("connect");
goto err;
}
printf("connect server(IP:%s Port: %d).\n", addr, port);
pid_t pid = fork();
if (pid > 0) {
// The parent process is responsible for sending messages.
while (1) {
bzero(send_buf, sizeof(send_buf));
char *str = fgets(send_buf, sizeof(send_buf), stdin);
if (str == NULL) {
perror("fgets");
goto err;
}
if (send(sock_fd, send_buf, strlen(send_buf) - 1, 0) < 0) {
perror("send");
goto err;
}
}
}
else if (pid == 0) {
// The child process is responsible for receiving messages.
while (1) {
bzero(recv_buf, sizeof(recv_buf));
if (sock_fd > 0) {
if ((recv(sock_fd, recv_buf, BUFFER_SIZE, 0)) <= 0) {
perror("recv");
goto err;
}
printf("[Recv from server %s:%d] : %s\n",
inet_ntoa(server_addr.sin_addr),
htons(server_addr.sin_port),
recv_buf);
}
}
}
else {
perror("fork");
goto err;
}
close(sock_fd);
return 0;
err:
close(sock_fd);
return -1;
}
编译后运行结果如下:
服务端启起来,等待客户端连接。 启动客户端,发送数据, 服务端接收数据。
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