[linux]小程序：UDP下client向server传输多个字符串

还是实验的作业~

一共需要两个文件，这是client

#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define ECHOMAX 255

int main(int argc, char *argv[]) {
    int sock;
    struct sockaddr_in echoServAddr;
    struct sockaddr_in fromAddr;
    unsigned short echoServPort;
    unsigned int fromSize;
    char *servIP;
    char *echoString;
    char echoBuffer[ECHOMAX+1];
    int echoStringLen=0;
    int respStringLen;
    int i;//for counting

    if (argc<3) {
        printf("Usage:%s <Server IP> <Echo Port> [<Echo Words>]
",argv[0]);
        exit(1);
    }

    servIP = argv[1];
    
    for(i=3;i<argc;i++){
        echoStringLen = echoStringLen + strlen(argv[i]);
    }
    if (echoStringLen > ECHOMAX)
        printf("Echo word too long.
");

    echoServPort = atoi(argv[2]);

    if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) <0)
        printf("socket() failed.
");
    memset(&echoServAddr,0,sizeof(echoServAddr));
    echoServAddr.sin_family = AF_INET;
    echoServAddr.sin_addr.s_addr = inet_addr(servIP);
    echoServAddr.sin_port = htons(echoServPort);

    for(i=3;i<argc;i++) {
        echoString = argv[i];
        if ((sendto(sock,echoString,strlen(echoString),0,(struct sockaddr *)&echoServAddr,sizeof(echoServAddr))) != strlen(echoString))
        printf("sendto() sent a different number of bytes than expected.
");
        }
    }
    echoBuffer[strlen(echoString)] = '';
    close(sock);
    exit(0);
}
    

这是server

#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define ECHOMAX 255

int main(int argc,char *argv[]) {
    int sock;
    struct sockaddr_in echoServAddr;
    struct sockaddr_in echoClntAddr;
    unsigned int cliAddrLen;
    char echoBuffer[ECHOMAX];
    unsigned short echoServPort;
    int recvMsgSize;
    int i;//for counting
    if (argc != 2) {
        printf("Usage: %s <UDP SERVER PORT>
",argv[0]);
        exit(1);
    }

    echoServPort = atoi(argv[1]);

    if ((sock = socket(PF_INET,SOCK_DGRAM,0)) < 0)
        printf("socket() failed.
");

    memset(&echoServAddr,0,sizeof(echoServAddr));
    echoServAddr.sin_family = AF_INET;
    echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    echoServAddr.sin_port = htons(echoServPort);

    if ((bind(sock,(struct sockaddr *)&echoServAddr,sizeof(echoServAddr))) <0)
        printf("bind() failed.
");

    for (;;) {
        cliAddrLen = sizeof(echoClntAddr);
        if ((recvMsgSize = recvfrom(sock,echoBuffer,strlen(echoBuffer),0,(struct sockaddr *)&echoClntAddr,&cliAddrLen)) < 0)
            printf("recvfrom() failed.
");
        printf("Handling client %s
",inet_ntoa(echoClntAddr.sin_addr));

    printf("Message: ");
    for(i=0;i<recvMsgSize;i++) {
        printf("%c",echoBuffer[i]);
        if(i==(recvMsgSize-1))
        printf("
");
        }
    }
    printf("
");
}

使用示例：

例如想要传输的字符串为Hello, world!

那么首先需要运行server：

./server 1500

1500是端口号（其实在普通用户的权限下，使用一个>1024的端口就可以）

然后运行client：（按alt+F2切换到新窗口运行）

./client 127.0.0.1 1500 Hello, world!

然后alt+F1返回原来的窗口，可以看到：

Handling client 127.0.0.1

Message: Hello,

Handling client 127.0.0.1

Message: world!